1 . After men landed on the moon in 1969, astronauts around the world had a problem — there were no other places they could go! Even today, the other planets are still too far away for astronauts to fly to. So, while rockets and robots can go to other planets, flights with astronauts have to stay closer to home, at least for the time being.

Therefore, since visiting the manned space programs have turned their attention to solving problems related to living and working in space.

For the past decade, NASA’s manned space exploration program has focused on the space shuttle program. During that time, NASA operated three space shuttles: Discovery Atlantis, and Endeavor. Unfortunately, two of NASA’s shuttles, Challenger and Columbia were lost through accidents.

Seven astronauts died in each accident. While the shuttle program was going on, the shuttles flew over 120 missions. These missions included putting satellites into orbit, photographing the earth, studying space, conducting experiments related to working in space, and connecting with various manned space stations in orbit. Today, however, Discovery, Atlantis, and Endeavor are no longer being flown. NASA retired its space shuttle program in 2011.

As well as putting rockets and space shuttles into orbit, several space stations have been put into orbit. In 1986, the Soviet Union launched the Mir space station. Mir stayed in orbit until March 23,2001. Over that time,104 astronauts visited the station to stay for various lengths of time.

The person who has spent the longest in space so far is Russian astronaut Sergei Krikalev Working aboard Mir and flying in other missions, Mr. Krikalev lived and worked in space for a total of 803 days,9 hours, and 39 minutes. That is more than two years in space.

Another space station, the International Space Station (ISS), is still in orbit today. The first part of this space station was launched in 1998.NASA added the final section to the ISS in 2010, officially completing the space station. In the long run, it is predicted that research done aboard the ISS will help scientists learn about living and working in space.

With hospitals filled up with COVID-19 patients, NASA has announced it will be delaying an upcoming satellite launch. The liquid oxygen     1     (need) to fuel the flight is also needed in hospitals,     2     doctors use the important resource to keep     3     (dangerous) sick COVID-19 patients alive.

“Medical oxygen is     4     priority (优先) of our members,” says Richard Craig, vice president of technical and regulatory affairs for the Compressed Gas Association.

A shortage of truck drivers     5     the certifications needed to transport the oxygen is only adding to the problem, and there are     6     (concern) about other rocket launches being pushed back as well.

At the recently held Space Symposium in Colorado, SpaceX president Gwynne Shotwell     7     (invite) anyone with access to liquid oxygen to reach out. “We certainly are going to make sure the hospitals are going to have the oxygen that they need but for anybody who has liquid oxygen     8     (spare), send me an email,” she said.

SpaceX founder Elon Musk tweeted that the shortage was “a risk,     9     not yet a limiting factor”. So far, 26 rocket launches     10     (plan) by the company.

I’m glad that you didn’t cheat in examinations.

Yours sincerely ,

Wang Lei

Detecting strong X-ray flares (耀斑) beaming from the center of a blackhole is nothing new. But detecting light signals from behind one is a different story. That’s     1     the force of gravity in a blackhole is so severe that nothing that goes in can come out. No scientist has managed     2     (find) light from beyond— until now.

In contrast     3     what their name implies, supermassive (特大质量的) blackholes can be one of the brightest sources of continuous light in the universe. Their     4     (extremely) gravity brings in all kinds of material around them. Little is known about supermassive black hole coronas, so scientists turned to blackhole I Zwicky 1,     5     lies 100 million light years from Earth, to investigate the beams shooting out.

Scientists     6     (detect) smaller X-ray “echoes” around the supermassive blackhole, in addition to the expected flares. The obvious light characteristics of these pulsing beams (脉冲光束) indicated that they were the same X-ray flares, but reflected from the backside,     7     (mean) the supermassive black hole’s gravity must have actually abnormal space-time, thus bending the beams around in a detectable direction by specialized telescopes. The     8     (finding), published in Nature, support a key     9     (predict) from Einstein’s theory of general relativity.

This is the     10     (one) research to confirm what the famous physicist predicted more than half a century ago.

8 . In the search for clean, renewable energy to meet our ever-increasing needs, wind power might seem to be the perfect option. Since ancient times, wind power has been used to move ships, pump water and grind grain. Around the end of the 19^th century, the invention of the wind turbine（涡轮机）made it possible to use wind to generate electricity. Now large-scale installations of wind turbines, called wind farms, create and develop clean electricity for people around the world. Yet despite the advantages that wind energy offers, challenges to using this renewable resource can be found.

The first advantage of wind power is that it truly is a renewable resource. No matter how much wind we use to generate electricity, we will never deplete the supply. This is its greatest advantage over non-renewable resources like coal or oil. However, wind does not provide a constant supply of energy. Even the windiest places on Earth have periods of calm. Without a strong wind, wind turbines are not able to produce electricity. That means that wind power isn’t feasible as a single source of electricity. It can only work with other sources that supply power.

Wind power is a clean source of energy, meaning it produces electricity without environmentally harmful missions. This is in contrast to conventional power plants that burn fuel to generate power, thereby producing pollution. But that isn’t to say that wind power doesn’t have an environment impact. The large spinning blades of a wind turbine can be fatal to birds and bats. The turbines also create noise pollution. The sound produced through normal operation can be annoying or disturbing to people that live near.

Fortunately, wind turbines are particularly well suited for areas far from homes and cities. The large towers that provide the base for the wind turbines also have a small footprint, which means that they don’t take up a lot of space. With all of the challenges of wind power, it obviously cannot be the sole solution for clean energy production. But the advantages of wind power generation shouldn’t be forgotten in the search for clean, renewable energy.

10 . E-cigarettes can damage vital immune system cells and may be more harmful than previously thought, a study suggests. Researchers found e-cigarette vapour disabled important immune cells in the lung and boosted inflammation (炎症).

The researchers caution against the widely held opinion that e-cigarettes are safe. However, Public Health England advises they are much less harmful than smoking and people should not hesitate to use them as an aid to giving up cigarettes.

The small experimental study, led by Prof David Thickett, at the University of Birmingham, is published online in the journal Thorax. Previous studies have focused on the chemical elements of e-cigarette liquid before it is vaped.

In this study, the researchers designed a mechanical process to mimic (模拟) vaping in the laboratory, using lung tissue samples provided by eight non-smokers. They found vapour caused inflammation and impaired the activity of alveolar macrophages cells (肺泡世噬细胞) that removed potentially damaging dust particles, bacteria and allergens. They sail some of the effects were similar to those seen in regular smokers and people with chronic lung disease.

They caution that the results are only in laboratory conditions and they are planning to do more research to better understand the long-term health impact the changes recorded took place only 48 hours.

Prof Thicket said while e-cigarettes were safer than traditional cigarettes in terms of cancer risk, they may still be harmful in the long-term. If you vape for 20 or 30 years, you can suffer from COPD (chronic obstructive pulmonary disease), then that’s something we need to know about.