2 . Most animal species in the world have developed some sort of natural camouflage that helps them find food and avoid attack. The specific nature of this camouflage varies considerably from species to species.

Camouflage develops differently depending on the physiology and behavior of an animal.    1    

An animal's environment is often the most important factor in what the camouflage looks like. The simplest camouflage technique is for an animal to match the "background" of its surroundings.

Since the ultimate goal of camouflage is to hide from other animals, the physiology and behavior of an animal's predators or prey is highly significant.     2    . For example, there’s no point in an animal replicating the color of its surroundings if is main predator is color-blind.

In addition to background-matching coloration, many animals have distinctive designs on their bodies that serve to conceal them. These designs, which might be spots, stripes or a group of patches, can help the animal in a couple of ways. First, they may match the pattern of "the model", the background of the animal's surroundings. Second, they may serve as visual disruptions. Usually, the patterns are positioned out-of-line with the body's contours (外形).     3    . This makes it hard for the predator to get a clear sense of where the animal begins and ends — the pattern on the body seems to nun of in every direction.

Other animals use a more aggressive sort of mimicry. Several moth species have developed striking designs on their wings that resemble the eyes of a larger animal. The back of the hawk moth caterpillar actually looks like a snake head, a frightening visage for most predators he moth would come across.

Mimicry is a different approach than ordinary camouflage, but it works toward the same end. By developing a certain appearance, an animal species makes itself a harder target for predators and a sneakier hunter for prey. As animal species evolve, they become more and more in tune with their environment.     4    . After all, being entirely overlooked by a predator is preferable to having to put up a fight.

3 . A breed of upstart apps is taking on an internet function that might seem unneeded or even ill—advised: helping teens talk to strangers.

Branded as “social discovery” services, these apps pitch themselves as alternatives to outlets that already specialize in online connections, like Facebook and Instagram. They say they are better at helping young users meet like —minded people outside their existing circles. And they say they have safeguards, such as separating users by age and using artificial intelligence, to protect against their appropriate or unsafe behavior that has plagued previous attempts to connect young people online.

Their user numbers suggest that, whether they succeed in striking the right balance, apps like Yubo and Hoop are tapping into a need among teens and 20 —somethings for new ways to branch out online.

“There is no place today to socialize online,” says Sacha Lazimi, the 26—year—old French co—founder of Yubo, which connects strangers with messaging and live streaming.

It is a counterintuitive statement for anyone who had seen teens sending Snaps rapid fire to their friends, responding to videos on TikToK, Face Timing for hours, or using Instagram. But Mr. Lazimi thinks those platforms allow for too much passive participation. “Snapchat, Instagram and Tik Tok are all about performance, content and individual”, he says.

Yubo features a swiping interface similar to that of Tinder. But Mr. Lazimi insists it is not adating app. The point, he says, is to facilitate communication between people all over the world who share mutual interests. Yubo isn’t present everywhere in the lives of American teens yet —and may be never will be—but the company says the app has 25 million users signed up, with nearly half of daily use now coming from America.

But some of these apps have also been the subject of safety concerns. Yubo has also faced its own safety challenges. In Florida, law—enforcement officially say they arrested a man who reportedly lured a teenager through Yubo.

In a statement, Yubo said that the prevention of child abuse has been a key priority for the past three years. “Yubo recognizes its responsibility in protecting young people using its service and has gone far beyond many of the main social media services.”

However, actually teens are doing more to protect themselves than many give them credit for, says Dr. Hinduja. “They are doing something to keep themselves safe or we would have strikingly more victimization than we do.”

5 . Recently I attended several meetings where we talked about ways to attract students and keep younger faculty members from going elsewhere. It seems higher education has become an industry of meeting-holders whose task is to “solve” problems — real or imagined. And in my position as a professor at three different colleges, the actual problems in educating our young people and older students have deepened, while the number of people hired — not to teach but to hold meetings — has increased significantly. Every new problem creates a new job for an administrative fixer. Take our Center for Teaching Excellence. Contrary to its title, the center is a clearing house (信息交流中心) for using technology in classrooms and in online courses. It's an administrative sham (欺诈) of the kind that has multiplied over the last 30 years.

I offer a simple proposal in response: Many of our problems — class attendance, educational success, student happiness and well-being — might be improved by cutting down the bureaucratic (官僚的) mechanisms and meetings and hiring an army of good teachers instead.

If we replaced half of our administrative staff with classroom teachers, we might actually get a majority of our classes back to 20 or fewer students per teacher. This would be an environment in which teachers and students actually knew each other. The teachers must be free to teach in their own way — the curriculum should be flexible enough so that they can use their individual talents to achieve the goals of the course.

Additionally, they should be allowed to teach, and be rewarded for doing it well. Teachers are not people who are great at and consumed by research and happen to appear in a classroom. Good teaching and research are not exclusive, but they are also not automatic companions. Teaching is an art and a craft, talent and practice; it is not something that just anyone can be good at. It is utterly confusing to me that people do not recognize this, despite the fact that pretty much anyone who has been a student can tell the difference between their best and worst teachers.

7 . The virtual world is full of opportunities to share with people around the world. It’s also a place where nothing is _________ and there are no “take-backs.” A lot of what you do and say online can still be found again even if you have _________ it, and it’s often something that is easy for others to access.

Research shows that a high percentage of teens receive _________ messages and requests when they’re online. These can be scary, strange, and even embarrassing. If you feel _______ by a stranger or a friend online, immediately tell an adult you can trust. It is never a good idea to _________. Any response you make is not only likely to make things worse, and might result in you saying something you wish you hadn’t.

If you are eager to let out angry comment on a message board or blog, it’s a good idea to wait a few minutes, _________ , and remember that your comments may stay up long after your temper has cooled and you have perhaps changed your mind. You might mistakenly find yourself regulated on social networks and this could _________ mean, insulting, or abusive comments toward someone else. But later you may _________ all that you have done. We’ve all heard of cyber bullying （网络欺凌）, but most people think online bullying is something people do _________. But sharing stuff or dropping random comments when we’re not face to face with someone can __________ just as much, if not more. And it can damage how others see you if they find out. __________ , a good rule to remember is that if you wouldn’t say it, show it, or do it in person, you probably shouldn’t do it online either.

Chances are that you’ve already checked your “digital __________ ” -- nearly half of all online users do. Try typing your screen name or email address into a search engine and see what comes up. That’s one way to get a sense of what others see as your online identity. In general, if you have questions about the trail you’re leaving online, don’t be afraid to ask a trusted adult. __________ , you might know more about the online world than a lot of adults do, but they have more life experience, which is something that can often be of more help. Your online identity is __________ in much the same way as your real-life identity, except that when you’re online you don’t always get a chance to explain your tone or what you mean. Thinking before you post and following the same rules for __________ behavior online as you do offline can help you avoid leaving an online identity trail you may over time come to regret.

It was very hot outside. The Chengdu Little Warriors were facing off against the Legendary Mighty Dragons of Beijing at a local indoor skating-rink (溜冰场). When I arrived, the Little Warriors, whose oldest player was eight years old, had just     1     their northern competitors. Near the lockers, a poster advertised hockey classes. Olympic     2     has begun to spread so far south that Chengdu now has nine skating-rinks and local hockey leagues for both kids and adults. It clearly shows China’s     3     to take the opportunity of holding the Olympics to promote winter sports across the country.

The 2008 Beijing Olympic Games were praised as a success by almost every     4    : the wonderful opening ceremony, the tight security, the large crowds of     5     volunteers, and Team China’s place atop the gold-medal rankings. Each aspect of the event signaled the country’s arrival as a world power, capable of competing with the best and winning.

If 2008 was about China getting a seat at the table, the 2022 Winter Olympic Games     6     a different purpose. China's status as a global power is no longer in question. Beijing 2022 will not be just a two-week sporting event but the     7     of a multi-year campaign to promote winter sports. “ We no longer need to put on shows of ten thousand people performing Tai Chi,” said Zheng Kan. “ Now we just want to show that we are relatable.”

While the audience for winter sports may still be a small, relatively rich group, it is growing. To prove his commitments (承诺) to winter sports, President Xi Jinping     8     a “ three hundred-million-person winter-sports plan.” The plan is aimed at raising China’s participation rate in winter sports from less than two percent to twenty-two percent. Some schools in Beijing have already introduced courses     9     to winter sports. A high-speed rail line that was opened at the end of 2019 cuts travel time between Beijing and Zhangjiakou, where many of the events will be held in 2022, to under an hour.

With all these efforts, the 2022 Winter Olympic Games are     10     to be wonderful and unforgettable.

9 . Patients often come into my office and ask, “How can I look younger?” While I always suggest healthy living — a balanced diet and regular exercise — in order to look and feel younger, I have never thought of facial exercises as part of that plan. That is, until a recent study, published in JAMA Dermatology (皮肤学), showed promising results that routine facial exercise may slow the merciless tide of time.

The theory behind the study originates from the fact that a major part of facial aging is due to the loss of fat and soft tissue, which leads to the growth and spread of wrinkles. If we can lift weights at the gym and enlarge muscles in arms, why couldn’t the same be done for muscles in our faces, therefore to create a more youthful face?

The concept of facial exercise is not a new one. A simple Internet search will produce a lot of blog posts and books on the subject, as well as various programmes that promise to be the next fountain of youth. What the JAMA Dermatology researchers did in their study, which was the first of its kind, was to examine this question from a more strict scientific aspect. They enrolled 27 women between the ages of 40 and 65 to perform daily, 30-minute exercises for eight weeks, and then continue every other day for a total of 20 weeks.

Dermatologists who did not know the participants were asked to rate their photographs before and after the exercise. The dermatologists found an improvement in cheek fullness and estimated the age of the participants at 51 years of age at the start of the programme and 48 at the end of the 20-week study. Furthermore, all the participants felt improvement in their own facial appearance at the end of the study.

While these results seem exalting, the study has some obvious limitations. Of the 27 patients involved, 11 gave up before completing the study. One reason may be that the programme was to time-consuming, clocking in at 30 minutes a day. The overall small size of the study also limits its generalizability to the larger population. In addition, there was also no control group, which would have helped reduce the possibility that this improvement happened by chance.

It’s also hard to draw conclusions about the longevity of these results. Probably the exercises must be continued to keep their effects. But for how long? And how frequently? Which exercises are most effective? Most studies are need to answer these questions.

Sports Icons(偶像) Who Lead a Change

China’s sports industry has entered a new era when the superstars themselves become the absolute focus of public attention. Compared with the gold medals and    1    the Chinese team has received, sports stars play the role of    2    people and improving the status of their sports in China. The following is an overview of those stars who once were, currently are or in the future will become milestones to change China’s sports demographics(统计数据).

Yao Ming: China’s Ambassador(大使)

Standing at 2.29 meters, Yao Ming used basketball to become one of the mainstream    3    ambassadors in modern China. He first played for his hometown Shanghai Sharks team in the CBA where he became a CBA champion ad Finals MVP in 2002. Soon afterwards, Yao was chosen by the Houston Rockets as the top overall pick in 2002. Over an eight-year span with the Rockets, Yao became an eight-time NBA All-Star. Besides his    4    in the CBA and the NBA, Yao was also a big reason for China’s continued dominance in the Asia basketball scene and their constant presence at world-level competitions. To this day, Yao remains one of China’s most    5    sports and cultural icons.

Liu Xiang: A Great Breakthrough

China’s world champion hurdler, Liu Xiang    6    the nation’s long-sleeping interest in track and field events after he became the first man to ever win a men’s track and field event for China. Before Liu won a gold medal in the men’s 110m hurdle race at the Athens 2004 Olympic Games and set a world record two years later, Chinese people had never shown such a strong interest in track and field events. Liu has become a significant player in China’s track and field events and the craze that has followed him is    7    to Yao Ming’s influence on China’s basketball. Both athletes prove how powerful a super sports star can be on    8    the development of a sport in China.

Li Na: New Image of China’s Tennis

Being the first Asian to win the singles title of a Grand Slam tournament, Li Na opened the door to tennis in China and even Asia. Her victory at the French Open 2011 was like a fairy tale and she has since been    9    as a national sports hero equal to Yao Ming and Liu Xiang. A record-breaking 116 million viewers from China tuned in to watch Li become the French Open champion, marking the start of a women’s tennis boom in a country    10    left out of the tennis conversation.