生物对环境的适应是生物界非常______的现象．

     Enough sleep is very important for people's health.Most of time we work in the day time and sleep

at night.Our body rests while we sleep.In the morning we are ready to work and play again.Our body

grows most while we are sleeping.Children usually need more sleep.We can learn our lessons better

after we have enough rest.Boys and girls at the age of eight or nine should sleep ten hours every night.

When we sleep,our body needs fresh air,so we'd better sleep with our windows open.While in bed

we must not cover our head.If you want to be strong,you must get plenty of sleep and fresh air.

1.When we sleep,our body is ________.

A.still working

B.resting

C.playing

D.dreaming

2.The best title for this passage is "________."

A.Boys and girls

B.Sleep

C.Rest

D.How to be strong

3.What does our body need when we sleep?

A.Fresh air.

B.Warm air.

C.Rest

D.Both A and C

4.________ can help children grow up well.

A.Enough fresh air

B.Enough rest and play

C.Enough sleep

D.Both A and C

5.We need to open our windows when we sleep,don't we?

A.No,we don't.

B.No,we needn't.

C.Yes,we do.

D.Yes,we need.

从交易品种看，中国人民银行公开市场业务不包括( )。

A．回购交易

B．现券交易

C．发行中央银行票据

D．发行国家债券

物质的性质决定物质的用途．请用下列物质的序号填空．

A．干冰   B．一氧化碳   C．氧化钙   D．尿素  E．亚硝酸钠

（1）为了防止某些食品受潮，常用______作干燥剂．

（2）在炼铁工业上常用作还原剂的是______．

（3）据报道，有些建筑工地食堂由于把______误作食盐，发生食物中毒事件．

（4）影视舞台上经常出现云雾缭绕的景象，产生这种景象可用的物质是______．

在许多社交场合，需要主动介绍自己给对方，一般情况下，有哪些注意要求？

(3 ) ( ) .

A．

B．

C．

D．