3 . It's easy to understand why early humans domesticated dogs as their new best friends. Domesticated dogs can guard against fierce animals and provide warmth during cold nights. But those benefits only come following domestication. Despite more than a century of study, scientists have struggled to understand what it was that caused the domestication process in the first place.

A new theory given by Maria Lahtinen, a senior researcher, might be able to explain this puzzle. She made this theory when studying the diet of late Pleistocene hunter gatherers in Arctic and sub-Arctic Eurasia. At that time, around 20,000 to 15,000 years ago, the world was in the coldest period of the last ice age.

In cold environments then, as today, humans tended to gain the majority of their food from animals. Nutritional deficiencies came from the absence of fat and carbohydrates, not necessary protein. Indeed, if humans eat too much meat, they can develop protein poisoning and even die. “Because we humans are not fully adapted to a diet that is carnivorous, we simply cannot digest protein very well,” Lahtinen says.

During that time, animals that humans killed for food would have been struggling to live, barely having fat and composed mostly of lean muscle. Using previously published early fossil records, Lahtinen and her colleagues calculated that the animals killed by people in the Arctic and sub-Arctic during this time would have provided much more protein than they could have safely consumed.

Under the tough circumstances of the Arctic and sub-Arctic ice age winter, sharing excess meat with dogs would have cost people nothing. The descendants of wolves that took advantage of such handouts would have become more gentle toward humans over time, and they likely went on to become the first domesticated dogs.

4 . Lixia, the Beginning of Summer

Lixia, also called the Beginning of Summer, is the 7th out of the 24 solar terms in China, which happens usually on May 5, 6 or 7.    1     People used to regard the day as the start of significant increase of temperature and thunderstorms. This day also marks the beginning of the peak season for the growth of plants. Lixia is not an official day that is celebrated by the public. It is just a sign to show the coming of hot summer so as to let people pay attention to keep away from hot weather.

Lixia egg is one of the typical foods. People use black tea leaves or walnut shells to boil eggs till they turn dark red.     2    , therefore, eating red eggs on this day symbolizes a kind of protection of heart and also provides people with enough strength to survive the coming hot summer days. Children usually hang nettings over their neck and put eggs in the netting. Playing with eggs can help children stay away from summer fever.     3    , which was very popular in the old days. People use red, yellow, black, green beans and peas, together with sticky rice to make a bowl of five-color rice. This color-rich rice will bring people good harvests in the summer.

Weighing people is traditional custom which dates from the Three Kingdoms Period.     4    , if the child was heavier than the previous year, it meant the child was becoming healthier and parents wouldn't have any worries for the hot summer.

After Lixia, the temperature is gradually rising and hot weather can be strain on your heart. As a result, people may easily feel tired during summer days. Having good rests becomes very important. Do not take up violent sports but do some slow activities.     5    . Besides, eating more fruits and vegetables and less hot and dry food can help tonify（滋补）your liver and kidneys.

5 . China still dumps most of the garbage it generates in landfills, which could pollute soil, water and air. Today, China is facing a problem similar to the one Japan faced in the 1970s, especially in its coastal cities which have a relatively high economic growth rate and a large population but comparatively limited land space, resulting in serious environmental pollution.

China has just started its garbage sorting journey, and it will take time for the people to make it a habit of sorting garbage at source.

Shanghai is among China's first cities to introduce garbage classification and also the country's most serious in its performing. Since July 1, 2019, Shanghai residents have been required by law to sort garbage into four different categories, or they could face fines. Individuals, including tourists, can be fined up to 200 yuan for failing to sort their waste properly, while companies and institutions can be fined up to 50，000 yuan.

The city government has set up online apps to handle sorting questions, and announced guidelines to address the "one-size-fits-all" method. The country is about to invest over 21 million yuan in the construction of garbage processing facilities to meet demands.

Following Shanghai, Beijing is also pushing ahead with garbage sorting legislation (立法) in the continual national action to get all of China sorting garbage. Not forced yet, the Chinese capital is already carrying out garbage sorting in more than 200 residential communities and it's trying to get more residents on board by making the system smarter. Now it's introducing artificial intelligence into its waste management system, by setting up little cameras in many sets of bins.

However, not every face can be recognized by the smart dustbin until you register (注册) for the system. Once registration is complete, users will scan a QR code on the bin, which then opens it up to allow for garbage disposal (处理). Now, each household gets one special QR code for throwing out waste. Here, the intelligent bins don't just calculate garbage weight, they also help residents gain rewards by collecting points through the special app.

China welcomes the age of compulsory garbage sorting with its cities revising laws on garbage classification. For Shanghai, sixty percent of the city is expected to implement garbage sorting by the end of this year, and 90 percent by 2020. Garbage sorting is, without doubt, a costly but worthwhile commitment. It is good for the environment and essential for the country's long-term development, and may finally turn out to be a promising industry as well.

7 . By the year 2050, a fifth of the world’s cities will experience unprecedented climate conditions and environments that currently don't exist in any major cities, according to new research. A team of scientists at the Crowther Lab in Switzerl produced the report, which described the climate for 520 major cities 30 years in the future.

The results showed that 77 percent of the world’s cities will experience a surprising change in climate conditions by 2050, and 22 percent of the 520 cities will see conditions that are not currently experienced by any existing major cities.

In China in 2050, the climate of Xi’an, in Shanxi province, will be similar to that of current day Maseru, the capital city of Lesotho in southern Africa, with the maximum temperature of the warmest month likely to increase by 4.5 C. Chongqing in southwest China will resemble the climate of Swaziland capital Mbabane, as the warmest temperature is predicted to rise by 5.1 C.

Scientists predict summers in Europe will get warmer by an average of 3.5 C and European winters will see temperature rises of 4.7 C. London's climate will be more similar to Barcelona, and Madrid’s to Marrakech.

The Crowther Lab hopes the analysis will motivate decision-makers to take necessary steps to prevent or address some of the climate impacts due to the threat of climate change. The report also found that cities in tropical regions will experience smaller changes in average temperature but will be controlled by shifts in rainfall regimes. This may lead to a noticeable increase in unexpected events, and severe droughts.

“Across all scientific fields, the greatest challenge in climate science is no longer the precise measurement of climate change impacts, but inspiring people to picture its actual effects in order to motivate action,” said Tom Crowther, senior scientist and founder of the Crowther Lab.

8 . 阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

Any bird that crossed his path would be eaten by Rex, a German shepherd. Rex    1    (rescue) from his previous shelter, where he was going to be put down after a biting incident. Last year, he    2    (eventual) arrived at Puriton Horse and Animal Rescue.

Geraldine was a goose abandoned by owners who could no longer put up     3     her. She wasn’t exactly the picture of     4    (warm), either, when she arrived at the same shelter three months ago. The dog and the goose were individually given labels like cruel and dangerous. Neither seemed particularly harmonious with humans or even members of their own species.

But when the two     5    (annoy) creatures were offered a chance to hang out together, something magical happened. They chased each other when first     6    (introduce), but Geraldine stood up for herself and that was that. They just fell in love with each other.

“I’ve been doing rescue work since 1997 and seen all     7    (kind) of strange animal behavior, but I’ve never seen anything like this,” said Sheila Brislin,     8    is the founder of the shelter. “It’s so amusing to see them because they love each other to bits. They are very affectionate. She just    9     (run) around alongside him all day long and whenever we take him for     10    walk in the woods she has to come, too.”

9 . Save the Animals

Animals are natural resources(资源) that people have wasted all through our history.

Animals have been killed for their fur and feathers(羽毛), for food, for sport, and simply because they were in the way. Thousands of kinds of animals have disappeared from the earth forever. Hundreds more are on the danger list today. About 170 kinds in the United States alone are considered in danger.

Why should people care? Because we need animals. And because once they are gone, there will never be any more.

Animals are more than just beautiful or interesting. They are more than just a source of food. Every animal has its place in the balance (平衡) of nature. Destroying one kind of animal can create many problems.

For example，when farmers killed large numbers of hawks(鹰), the farmers’ stores of corn and grain were destroyed by rats and mice. Why? Because hawks eat rats and mice. With no hawks to keep down their numbers, the rats and mice multiplied(繁殖) quickly.

Luckily, some people are working to help save the animals. Some groups raise money to let people know about the problem. And they try to get the governments to pass laws protecting animals in danger.

Quite a few countries have passed laws. These laws forbid(禁止) the killing of any animal or plant on the danger list. Slowly, the number of some animals in danger is growing.

10 . A woman from the United Kingdom was injured when she protected her friend’s dog from an attack of a coyote (郊狼). Jessica Jones and the dog, named Roxy, may have found a coyote’s den (巢穴) in an overgrown area near the backyard of the friend’s home in Reading, Massachusetts, before the attack, according to the Reading Police Department.

“Our early finding shows that this coyote was acting to protect itself and its babies, so we do not believe there is any threat to the public,” Reading Police Deputy Chief David Clark said.

After the coyote went after the dog. Jones used her arm to protect Roxy and then “hit the coyote in the face” before running off with Roxy. Jones was injured but Roxy was not hurt in the scuffle.

“I told my family that Jessica was pretty cool and that they’d enjoy having her come stay, but I didn’t think any of us could have possibly expected how grateful we would end up being,” Jones friend, Grace Tully said. “Coyotes have come near and in the yard but never got too close.” Other neighbors have reported seeing coyotes in the area but have never reported any attack.

“The presence of coyotes themselves is no cause for concern, as they are naturally afraid of people,” the police said. To avoid attracting coyotes, the police advised people to put their waste in well-covered containers, keep bird feeders clean and feed pets indoors.