1 . Thanks to their evolutionary ancestry, domestic cats are, actually by their nature, more independent than dogs. Our cats, whose wild ancestors didn’t enjoy living in social groups as dogs do, _______, during the process of domestication, gradually developed the capability to form social relationships not just with other cats, but also with people.

Although independent cats may not _______ upon people to gain security as dogs do, they show affection for their guardians and seem to attach importance to the _______ of their human companions. Their strong attachment to humans is partly _______ by their experiences of being cared by people as a kitten. Cats behave towards humans in the exactly same way that they respond to their feline friends, so the secret of whether your cat feels _______ to you lies in their behaviour.

Cats have successfully gained an edge for their outstanding ability to communicate with other cats over long distances and even when no longer _______ present. Our pet cats have _______ this “supersense” and depend heavily on this form of communication. Particularly, cats use scent to identify members of their social group or family, by sharing a group scent profile. Cats have specific scent glands on their flanks, head and around their ears, and often rub their heads against people and objects that are familiar and _______. The soft sensation you feel against your calves is actually your cat _______ you as a friend and is a huge compliment.

One of the most signs that your beloved pet is keen on you, is the way your cat greets you. When cats greet members of their social group, they ________ to show signals to indicate friendship and a desire to move closer. Also, Cats show these signals to humans. Rolling over and________ their vulnerable under belly to you is another distinct gesture that a cat has ultimate faith in you.

Besides, your cat might also be secretly signalling their affection by changing the way they look at you. When cats ________ strange humans or other cats they aren’t familiar with, they usually greet them with an ________ stare. But they are more likely to slowly blink at cats they have a good relationship with. Research indicates slow blinks are ________ a positive emotional state and can be a sign of trust, contentment and affection, ________ to a genuine human smile.

3 . Since the start of the Space Age, private­sector (私营部门) leaders have been issuing warnings that a centralized model would damage progress on public and, especially, commercial priorities in space. For example, Ralph Cordiner, the one­time CEO of General Electric, foresaw much of the space development while forcefully arguing that, eventually, space’s “development shall be under our traditional competitive _________ system.”

The economic logic for the centralized model was clear, and for several decades it has _________ its goals. Public goods such as national security, national pride, and basic science are typically _________ if left to the market, and NASA (美国宇航局) was founded to provide them during the Cold War. Its command­and­control structure grew naturally from that _________.

Under this model, the United States has been the leading space power and NASA has occupied the technological frontier. The success of the Apollo missions, including the 1969 moon landing, inspired grand _________ of what would come next. In the early 1970s, studies of space colonization and diversified space­based economies _________.

But after the last of the Apollo missions in 1972, NASA — and thus the US space sector — struggled to find a second _________ in its space script. Part of the reason was that the tight connection between the Apollo program and competition with the Soviet Union made NASA’s budget vulnerable (脆弱的) to the sense that the mission had already been accomplished. Apollo astronaut Buzz Aldrin said, “After the Apollo lunar missions, America lost its love of space — there was no concentrated _________ and we didn’t have any clear objectives”.

When NASA decided that its next emphasis would be on the Space Transportation System, better known as the Shuttle, it applied largely the same _________ approach it had used in the 1960s. The first flight of the Columbia space shuttle was in 1981. Successive shuttle flights enabled two decades of achievements, including the construction of the International Space Station (ISS) and Hubble Space Telescope, which __________ American technological competence.

After two tragic accidents, with the Challenger shuttle in 1986 and the Columbia shuttle in 2003, momentum(势头)turned away from the Shuttle and the centralized model of space it __________. The shuttle program was cancelled in 2011, leaving the United States in the __________ position of not being able to launch humans from domestic soil.

An instructive contrast is provided by the __________ the US government took to the development of the commercial satellite market. In 1962, Congress created COMSAT, a for­profit, private corporation owned by common shareholders and a group of telecommunications companies. NASA was officially charged with providing __________ advice to COMSAT, and the agency was given responsibility for COMSAT’s launches. The idea behind this public­private __________ was to employ the expertise of NASA to jump­start a private communications satellite industry. It led to the rapid deployment and use — for both public and private purposes — of the vast range of satellites that dominate the space economy today.

5 . The Delight of Bird-watching

It is springtime, and the city feels especially glorious. If we were to reflect on what has brought us joy during this challenging time, birds would probably be enjoying a top ________ on the happy list for many. Especially those we saw outside of our windows - or, in New York City, on the street.

Three species in particular ________ the sidewalks, tops of buildings, fire escapes, window ledges, and air conditioners: house sparrows, pigeons and starlings (椋鸟). All of these species are ________. When these species were first introduced, the scientific fields of ecology (生态学) and conservation were ________ nonexistent, and now we know that for pest control (虫害防治), this was a terrible idea. But I would add a qualifier to that terrible idea by calling it “a wonderful, awful” idea.

I have been studying starlings in New York City since 2016. I do so formally in museums and labs, but in between my research I watch them ________ on the street. I was initially fascinated by their adaptability to the ________ landscape, especially their ________ flexibility. They will eat a pile of yellow rice on Columbus Avenue, a soft pretzel on Central Park West, and a flattened apple pie in the parking lot of a Costco in Queens. Pigeons and house sparrows often hover and hop around them, but cannot compete with their ________. For a bird, they are good at walking on the ground.

The sounds they make are so ________ that you might not recognize that they are coming from the same species. If you listen closely, you can hear their up-and-down whistling, whirring, and even an early video game laser-like sound. You may not consider it ________ enough to be called a song, but it is a song nonetheless. When you stare at them, as I have many times, they never even appear to look at you, but they obviously see you because they respond incredibly rapidly to absolutely any movement or disturbance. They are off ________, always faster than I can draw my phone out in order to grab a good picture.

Sometimes, I wish that I did not know about what else they do across the country, and could just enjoy watching them in a quiet ________. And I wonder if you can know about their paths of ________ and still appreciate aspects of their behavior.

At times this winter, nothing in the built environment even came close to ________ me of life or the natural world. And then way up in that bit of sky, beside the water tower, I spotted five of them. I’d know their triangular wings, and their quick and suspicious behavior, anywhere. As they flew up and ________, they left in their wake the hope of bluer skies and future springtime.

6 . Bringing Mosquitoes Under Control

Every year, hundreds of thousands of people die of mosquito-borne diseases like malaria and dengue fever. Drug treatments are ________, and, despite decades of effort, vaccines have, for many of these diseases, proven to be difficult to develop.

It is better, then, to stop these infections happening in the first place by ________ doing away with the mosquitoes that carry the diseases. CRISPR-Cas9, a new and powerful genetic-engineering process, could help to do just that.

Craig Montell, of the University of California, and his colleagues have used CRISPR to ________ an existing control method called the sterile insect technique (SIT), which involves releasing lots of sterilized (绝育的) males into the wild. Females that mate with these males produce no young. ________ releases can reduce populations dramatically. SIT has been used in North America to eliminate screwworm flies, an agricultural pest.

SIT has been tried on mosquitoes, too, but with less ________. One reason seems to be the side-effects of the procedure. To sterilize them, males are exposed to poisonous chemicals. This works, but it damages them in other ways, too. The result can be sickly individuals that ________ to compete in the mating game with wild mosquitoes.

Montell and his colleagues hoped that CRISPR might offer a(n) ________. Their first step was to look for genes which affect fertility (可繁殖性) in mosquitoes. They began their hunt in fruit flies and ended up focusing on a gene that, when ________, made male fruit flies sterile. The gene was present in a similar form in their target mosquito species, Aedes aegypti, which passes on, among other illnesses, yellow fever, dengue and the Zika virus. Disabling the ________ gene in male Aedes likewise left them infertile. ________, the genetic changes involved did not appear to affect the engineered mosquitoes in any other way. On every measure of ________, they performed as well as wild mosquitoes.

________ the details are not fully understood, once female mosquitoes have mated a few times, they become unwilling to do so again. Mating with an infertile male is, therefore, not only fruitless in itself, but should also leave a female less interested in ________ males.

There is more work to be done before field trials, but having established the ________, Montell is excited to see where the work might lead. That the engineered males leave no young means that there are fewer worries surrounding any ________ consequences which might arise from the release of millions of genetically edited creatures into the environment. And that the target gene is found in both fruit flies and Aedes suggests it is likely to exist in other disease-carrying mosquitoes, too.

7 . Southern long-finned pilot whales are marine mammals with a lot to say—and they may use vocalizations (发声) to outsmart a deadly enemy.

Cetaceans (鲸类动物) such as whales and dolphins communicate through sound to find food and mates, to navigate and to interact socially. Their vocalizations _________ between species and within communities. The animals can mimic (模仿) artificial noise such as sonar, but nobody had previously recorded them _________ other cetaceans’ sounds. A new study, however, found overlap in the cetacean sound book.

Researchers listened to 2,028 vocalizations of long-finned pilot whales off the coast of Australia, the first time sounds from the species in this region have been _________ described. They were surprised to hear 19 instances of vocalizations that resembled those of orcas—the whales’ oceanic _________. “We found some calls that are, to the human ear, _________ to the killer whale calls in the same area,” says Christine Erbe, an expert in Marine Science and Technology.

Pilot whales and orcas, the two largest species of cetaceans, are often seen in the same _________ and are similar sizes, and both live in social groups. Orcas compete for food with long-finned pilot whales and are _________ their predators (猎食者) .

_________ from orca stomachs shows they do occasionally eat pilot whales. But pilot whales can mob and chase orcas away, the only cetaceans seen _________ themselves from their predator in this way.

Mimicry could serve as an __________ defense: “One theory is that if they use similar sounds, they may not be recognized as prey,” Erbe says. Pilot whales hunting or eating orcas’ food remainders might go __________ if they use orca-like calls. “This is all underwater, where light travels really poorly,” she adds. “So these animals __________ sound for detecting their prey and predators and for navigating.” Long-finned pilot whales have shown an ability to __________ between orca calls with different meanings.

Additional work would __________ whether mimicry is actually occurring. Researchers could pair their listening data with direct observations of the animals’ interactions in the wild or perhaps even play orca sounds and watch the whales’ __________.

8 . Country diary: a chainsaw massacre in the alder woods

On an overcast, drizzly afternoon at Durham Wildlife Trust’s low Barns nature _________ alder provided the brightest splash of color in the _________

A tree had been felled and sawn into _________. Chainsaw wounds on this species can look like a massacre, because soon after the timber is cut, it turns a lurid shade of red, almost like blood, in stark contrast to the battleship-grey bark, _________ those wounds, which briefly _________ raw meat, fade to orange and finally to chestnut brown.

When this reserve was established half a century ago, around old gravel pits (采沙场), some moisture-loving alders were planted to help _________ a bare, windswept site. Alder wood is one of the finest sources of charcoal, and the plantation trees are old enough now to be coppiced, to produce barbecue fuel.

There is also an important natural alder wood here, created by a cataclysm almost two and a half centuries ago, which led to the designation of the reserve as a site of special scientific interest.

The Great Flood of 1771 _________ Weardale, washing away bridges all the way to the coast. When the water subsided, the course of the River Wear had _________ half a mile south, and the old riverbed became what is now the reserve’s Long Alder Wood, the finest example of its kind in the region.

When it sometimes floods, this tangle of gnarled（苍劲嶙峋的） trees has a _________ of the Florida Everglades（佛罗里达大沼泽） about it, with mossy, fallen trunks sinking back into the ooze (淤泥). Year round, there are wonderful __________ to watch birds from an embankment level with the tree canopy. This afternoon an acrobatic flock of about 30 goldfinches（金翅雀）__________ and chattered through the twigs, feeding on tiny seeds that fall from the woody cones.

Sadly, since the mid-1990s, another__________ has befallen this locally __________ woodland: alder dieback disease has killed around half the mature trees. Coppicing is leading to some regeneration, though in this precious __________ dead timber is allowed to lay where it falls, reserved for the needs of a __________ community of fungi, invertebrates and woodpeckers, rather than back-garden burger-flippers on summer evenings.

9 . China becomes a world leader in clean technology by fighting environmental pollution, sharing experience.

Erik Solheim, former executive director of the United Nations Environmental Programme, said he is __________ with China’s phenomenal achievements over the past decade in fighting environmental pollution and climate change, and in its march toward __________ development.

This is very __________ to his Twitter followers. Solheim’s latest tweets include one about China ranking first globally in planted forests and forest coverage growth, __________ a quarter of the world’s new forests in the past decade; one about China producing 60 percent of global solar energy last year and 80 percent of solar panels; and another highlighting the fact that 80 percent of the world’s new offshore wind capacity was installed in China last year.

He believes that it’s time for the rest of the world to __________.

For Solheim, who is also the former Norwegian Minister of the Environment and Minister of International Development, China’s achievements on the climate and environmental fronts all started with its fight against__________.

“People wanted to see beautiful skies over their cities,” he told China Daily. “The __________ fast reduction in air pollution in Chinese cities over the last decade shows how fast China can act. This has now spilled over into renewable energy, nature protection, electric mobility, tree planting and a lot more. Today, China is the world leader in all __________ technologies.”

The latest __________ from China’s Ministry of Ecology and Environment prove Solheim’s observations that the country is rapidly switching to a more sustainable path.

Minister of Ecology and Environment Huang Runqiu told a news conference on Sept 15 that the country’s toughest measures and greatest progress on the ecological and environmental front have occurred in the last decade.

He said that __________ painstaking efforts to combat pollution, clear waters and blue skies have become more commonplace.

While poor air quality used to be a source of frequent public complaints, the average __________ of hazardous airborne PM2.5 particles dropped from 46 to 30 micrograms per cubic (立方的) meter between 2015 and last year.

About 87.5 percent of days last year were rated as having good air quality, up 6.3 percentage points from 2015, making China the country with the biggest __________ in air quality in the world.

In the last decade, the __________ of water at or above Grade III in the country’s five-tier water quality system rose 23.3 percentage points to 84.9 percent, close to the levels in developed countries. Carbon intensity, or carbon emissions per unit of GDP, has declined by 34.4 percent, with coal __________ for 56 percent of total energy consumption, compared to 68.5 percent a decade ago.

China has has legislated or revised roughly 30 laws and regulations, some of which focused on water resource protection, including the Water Pollution Prevention and Control Law, which was modified in 2017, and the Yangtze River Protection Law, which __________ last year.

10 . It took brave European explorers less than 300 years, between 1420 and 1713, to establish that all the seas of the world formed an enormous and continuous ocean. This discovery encouraged them to _____ into areas which hadn’t been charted until then. With the discovery of new lands, new trade routes were _____. In many parts of the world, colonies and settlements were established and many odd-looking products were brought back to _____, arousing great interest and _____ wealth.

It was probably the irresistible desire for wealth that _____ persuaded Europeans of the fifteenth century to _____ their legendary dangers and explore further out into the open seas. They were also _____ by the love for their countries. Many explorers wanted to serve their kings and countries as well as gain personal _____ from their exploring.

The most effective way of gaining wealth was through _____. Silk, gold, silver and ______ stones, and more importantly spices, such as gingers and peppers, were the most profitable trade goods in Europe. Spices were of the greatest ______ because they enabled the Europeans to make their winter diet of salted meat more delicious. These items were ______ mostly from the East by a difficult overland route. The Italian ______, who bought goods from the Arabs of Alexandria, controlled the trade along this route. Other countries of the Mediterranean ______ the wealth which this trade generated and they were ______ to discover new routes which would allow them to share in it.