形填空在英语六级各类试题类型中是比较难的类型，各位考生在备考时要多加练习。本文提供练习一篇，助同学们备考。
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.C 3.C 4.B 5.D
6.C 7. A 8.D 9.A 10.B