题目内容：

    All animals—from humans to birds，worms and crocodiles—sleep，however，not all species sleep alike. Scientists have long puzzled over which aspects are truly fundamental. Now a new study on lizards(蜥蜴)suggests that sleep states once thought to occur only in mammals and birds have much older evolutionary origins.

Scientists had long doubted that birds and mammals are the only vertebrates(脊椎动物)to experience rapid eye movement(REM)，a sleep state in which the body is mostly immobile but the brain is overworking. During REM sleep，the brain produces high-frequency waves of electrical activity and the eyes turn suddenly from time to time. In humans，REM is closely linked to dreaming. REM is a pattern of slow-wave sleep，a state in which brain activity weakens and the waves become more consistent. This slower state is widely thought to be important to memory formation and storage.

“But scientists who looked for signs of REM and slow-wave sleep in reptiles(爬行动物) have had‘confusing’results，”says Gilles Laurent，a neuroscientist at the Max Planck Institute for Brain Research in Frankfurt，Germany. So he and his colleagues had planned to examine how the lizards—a common pet in Germany use visual information to chase treats. Using camera，the team found that the sleeping lizards’eyes twitched during the REM-like stage，just like other animals. They also found a very familiar pattern within the slower phase of the lizards’brain waves. Some scientists believe these waves help transform new information into memories by replaying past events quickly.

Although more studies are still needed to determine whether the function of these brain wave patterns is the same across species，the results suggest that these REM and slow-wave sleep patterns could date all the way back to the common ancestor of reptiles，birds，and mammals.

1.What does paragraph 2 mainly talk about?

A.The origin of human dream.

B.The definition and effect of REM.

C.The features and course of memory.

D.The advantages and disadvantages of REM.

2.Which of the following can best replace the underlined word“twitched”in paragraph 3 ?

A.opened wide B.moved quickly

C.stayed closed D.kept still

3.How does the lizards’brain waves turn information into memories according to some scienfists?

A.By increasing their frequency slowly.

B.By changing their pattern occasionally.

C.By playing back the past events quickly.

D.By connecting visual information effectively.

4.What can we infer from the last paragraph?

A.The function of the brain wave is the same.

B.All the animals have the common ancestor.

C.The sleep pattern of all the animals is the same.

D.The study about sleep pattern has a long way to go.