A study of sleep in sparrows suggests the relationship between sleep and the ability to learn may be more complicated (复杂) than realized．

    Niels C. Rattenborg of the University of Wisconsin—Madison wanted to find out how the sparrows were able to deal with getting so much less sleep．He and his team brought eight wild birds into a lab and watched them for one year．They invented a game to check how well the birds could learn．In the game, the sparrows had to peck (啄) three buttons (按钮) in a certain order to get a food treat．The scientists discovered that the birds' ability to learn the right button order depended on (依靠) two things, the time of year and the

amount of sleep the birds had．

    During the migration (迁徙) season, the sparrows were restless at night and got much less sleep than usual．Even so, they were able to understand how to get the food quickly as if they'd had a regular night of sleep．Outside the migration season, they found the sparrows that got less sleep than usual had much more difficulty learning how to get the food treats than birds that had a regular sleep．

    The results show that the sparrows can deal with much less sleep during the migration season than usual．If scientists can find out why, they may learn from sparrows and find ways of helping people deal with getting much less sleep．Until scientists fully understand the relationship between sleep and learning, it's better to get plenty of sleep when preparing for an exam．

Marvel is one of the most popular companies in the world. As early as 1939, a  {#blank#}1{#/blank#}called Motion Pictures Funnies Weekly was on and Namor the Sub-Mariner was the first superhero in Marvel. So far, these have been many famous superheroes. Among them, I like Iron man best. In Iron Man I . he is a  {#blank#}2{#/blank#} person with lots of money. Because he has experienced dangerous situation, he  {#blank#}3{#/blank#}to protect himself and other people with his wisdom(智慧). After he makes this important decision, he spends most of his free time  {#blank#}4{#/blank#}battle suits with high-tech. From then on, he starts to do good thing around the world  {#blank#}5{#/blank#} . In the end of the movie, he reveals his identity to the whole world in an interview.

They hang from trees.They float in rivers and oceans.They are piled up in landfills（垃圾填埋场）.Our frequent use of plastic products has，for many years，been a leading cause of serious environmental problems in the world.Last month，China drew up new guidelines（指导方针）aiming to bring plastic pollution under control across the country in five years' time. 

According to the new guidelines，the ban（禁令）on the use of non-biodegradable（不可生物降解的）plastic bags will have been applied to cities including Beijing and Shanghai by the end of this year.Other sources of plastic garbage will have been banned in these cities by the end of 2022.And that rule will have extended nationwide by late 2025. 

Fortunately，China will not start from zero.Late last year，the country announced a national standard for biodegradable plastic shopping bags.It is technologically prepared for their production.Some regions have gained valuable experience that others can learn from.For example，Jilin province is leading the way by providing eco-friendly（环保的）shopping bags in some local supermarkets. 

Given the size of China's consumer market，one main obstacle（障碍）is the large number of plastic items that are being used by restaurants and e-commerce（电子商务）platforms.It's estimated that nearly 25 billion plastic bags were used for deliveries in 2018.Most of them were rarely reused. 

However，most Chinese people welcomed the government's effort to reduce the use of plastics."Beijing is thinking about the problem seriously，"said Tang Damin，a member of Greenpeace East Asia in Beijing.He added that the policy could be far more effective（有效）by using incentives（激励）such as a deposit（押金）return program on plastic products.

Hi! I'm Gina. This is my friend, Lily. And these are the photos from her. 

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This is a photo of her family. They are her parents. The boy is her brother. He is a student, too. 

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It is big and tidy. Only 15 desks and chairs are in it. The big desk is the teacher's. On it you can see four books. They are the teacher's, too. 

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Frank is its name. It is three years old. But it's very small. It is white and black. She plays with it every day. 

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Look! Some things are on her desk. The red pen is from her brother. And the red skirt is from her grandparents. She likes them very much.