The popularity of Chinese video-sharing social networking service TikTok continues to grow among young people in the United States, especially teens and young adults.

The service lets users create and share short videos, many of     1     are within 15 seconds. The TikTok app offers a wide choice of sounds, brief parts of songs and special effects tools     2     (produce) a video. Videos often include popular songs from famous     3     (art) and TikTok has even helped begin the careers of new music stars.

TikTok     4     (consider) a competitor to video-sharing app Snap chat, as well as Facebook’s Instagram service, which also mainly interest young users with photos and videos centered     5     (large) on fashion, pop culture and humor.

Last year, TikTok was the     6     (two) most downloaded app from Apple and Google stores.     7     was said that people have downloaded the TikTok app 1.65 billion times.

While TikTok has continued to grow, some experts and parents have expressed concerns about videos     8     (appear) on TikTok that might be     9     (harm) to young users.     10     this reason, they urge parents to monitor what their children watch on TikTok and suggest that only those over 16 should have access to the service.

We grew up with the familiar toy bricks (积木) that gave us the imagination to build towers and castles. Generations have been attracted by this toy that lets children and adults alike create anything and everything. But     1     over 200 million sets being sold a year in over 100 countries, the question remains-where did Lego actually come from?

Lego was born from the creative mind of Danish carpenter (木匠), Ole Kirk Christiansen, back in the early 1930s. He established a small business in Denmark. He and his team     2    (build) a variety of household goods like ironing boards along with wooden toys. The Lego name     3    (adopt) in 1934, formed from the Danish words “Leg Godt” or “play well”,     4     means “I study” or “I put together” in Latin.

Christiansen’s company continued to make wooden toys until 1942 when fire struck-the entire Lego factory burned to the ground.     5     (will) to give in, the factory was rebuilt and the production line restarted soon after. By 1954, Christiansen’s son, Godtfred,     6     (become) the junior managing director of the Lego Group. It was during his conversation with an overseas buyer     7     he was struck by the idea of a toy system.

For over 30 years, the Lego Company made only toys and related goods. Then, in 1968, the company opened its     8     (one) Legoland in Denmark. Combining the Lego building bricks with a computer, the Robotics Invention System 1.5 is now the most advanced toy in the Lego Company, which is targeted at     9     (use) aged twelve and above, and that includes any parents or grandparents that want to join in.

Now the Lego Company is expanding its production lines to include lights, cameras and so on. Lego Company has done a lot to entertain many children     10     (globe).

【推荐3】Many teachers believe that hands-on experience is the     1    (good) way to learn. A group of students in the United States are putting that belief to the test. They     2     (success) designed and built a robot for discovering unexplored mines     3     the bottom of the sea. Students made the robot     4    (answer) a challenge from the U.S. Department of Defense.

The students recently tested the underwater vehicle     5    (call) PerseusⅡin a 95-meter-long tank of water at the Stevens Institute of Technology.

The robot costs about $15,000 to build. The students use a video game control to direct     6    (it) movements in the tank. What’s more, devices known as Japters     7     (able) the robot to go up, down and toward its target in the water. Video cameras on the robot send images back to a computer through a 13-meter-long cable. PerseusⅡ,     8    the students worked up to 20 hours a week to design and build, also has     9     set of lasers (激光), which are used to measure the size of an object.

DeLorme supervised the project from     10    (begin) to end. He says the specialized requirements of robots were demanding.

Polar bears live in such environment that is too cold for most animals. For much of the year, they live and hunt on the     1     (freeze) Arctic sea ice. Nature has prepared them for the cold conditions but nothing has prepared them for the danger     2     threatens their only home.

Polar bears’ world is melting. Polar bears     3     (suffer) in a warmer world are in danger. Studies show that the polar ice     4     (reduce) by 9.8% every ten years since 1978. At present, about 20,000 to 25,000 polar bears live in the Arctic. Polar bears depend on the sea ice for their     5     (survive). “The sea ice is more than just the platform that the bears walk     6    .” says Andrew Derocker, who studies North American polar bear population. “Without it, they can’t exist.”

Some melting and refreezing of the polar ice is nature. But in     7     warmer world, these cycles speed up, and bears have     8     (little) to hunt.     9     (normal), they have three months in the spring when they gain more weight and the extra fat     10     (use)   later, when the bears are not actively hunting. Therefore, it’s urgent to protect the environment and maintain the ecological balance.

Do you know human-wildlife conflict?

Human-wildlife conflict, referring to direct interactions between humans and wildlife with negative outcomes, costs the     1    (globe) economy billions of dollars annually. Worse still, it     2     (threat) human lives and causes many species to die out. These conflicts     3    (large) result from humans and wildlife seeking limited resources in the same landscapes and often have many     4     (expect) consequences. As a matter of fact, both extreme climate events and climate change have the potential to influence the interactions between humans and wildlife. Serious climate events can bring about rapid changes in resource availability,     5    may drive strong responses in animals and people. The     6    (compete) between the two grows tougher as a consequence. Droughts     7     particular have caused some of the most visible conflicts. Despite the gravity of these conflicts, climate change is making human-wildlife conflict even     8    (serious). With people and wildlife sharing crowded spaces and limited resources, human-wildlife conflict is rising in frequency. Many people,     9    , still haven’t really realized how complex and severe the problem is. Therefore,     10    (protect) wildlife and humans alike, it is vital that a wide range of research and institutions should consider the role of a changing climate in shaping the complex dynamics of conflict.