Sleep is divided into periods of so-called REM sleep, characterized by rapid eye movements and dreaming, and longer periods of non-REM sleep. 1 kind of sleep is at all well-understood, but REM sleep is 2 to serve some restorative function of the brain. The purpose of non-REM sleep is even more 3 . The new experiments, such as these 4 for the first time at a recent meeting of the Society for Sleep Research in Minneapolis, suggest fascinating explanations 5 of non-REM sleep.

For example, it has long been known that total sleep 6 is 100 percent fatal to rats, yet, 7 examination of the dead bodies, the animals look completely normal. A research has now 8 the mystery of why the animals die. The rats 9 bacterial infections of the blood, 10 their immune systems-the self-protecting mechanism against diseases-had crashed.

1. [A] Either [B] Neither [C] Each [D] Any

2. [A] intended [B] required [C] assumed [D] inferred

3. [A] subtle [B] obvious [C] mysterious [D] doubtful

4. [A] maintained [B] described [C] settled [D] afforded

5. [A] in the light [B] by virtue [C] with the exception [D] for the purpose

6. [A] reduction [B] destruction [C] deprivation [D] restriction

7. [A] upon [B] by [C] through [D] with

8. [A] paid attention to [B] caught sight of [C] laid emphasis on [D] cast light on

9. [A] develop [B] produce [C] stimulate [D] induce

10. [A] if [B] as if [C] only if [D] if only

参考答案：1.B 2.C3.C 4.B 5.D 6.C 7.A 8.D9.A 10.B