Ellen Sims is an 18-year-old college student. She has an important history exam tomorrow morning. Ellen is going to study all night. She is not going to      at all. Many college students, like Ellen, do this often. They think that in the morning, they will     everything that they studied the night before. Ellen thinks that this is a good way to study, but many doctors      . They say that sleep is very important for memory and brain development.
Scientists at Harvard Medical School in the USA studied sleep and memory. They studied 24 people. First, they asked the people to look at a picture and        it. At night, they put the people in      groups of 12. Group One went to sleep. Group Two did not. A few days later, scientists showed some        to both groups. They asked the people to find the picture they    before. The people in Group Two did not do so       as those in Group One. It wasn’t      for them to remember the picture. What happened? Scientists say that sleep     our memory. After we learn something new, sleep helps us remember it. And when we don’t sleep, we can     new things.
Scientists say that many teenagers, like Ellen, sleep too     They go to school and work, too. They also       time with their friends. They’re always      and they think sleep isn’t important. But scientists say the brains of teenagers are still       , and sleeping is a very important part of the development. When teens sleep less than six hours, they can’t think clearly. That is not very helpful for a student who is taking an exam.

A．study B．work C．sleep D．think

A．learn B．use C．forget D．remember

A．discuss B．disagree C．dislike D．discover

A．remember B．sell C．hold D．copy

A．two B．three C．four D．eight

A．pencils B．pictures C．books D．newspapers

A．remembered B．threw C．saw D．drew

A．nice B．glad C．good D．well

A．hard B．clear C．easy D．possible

A．steals B．helps C．takes D．worries

A．forget B．understand C．grasp D．lose

A．many B．much C．little D．few

A．cost B．spend C．take D．pay

A．lazy B．relaxed C．worried D．busy

A．developing B．getting C．cloning D．dreaming