下列关于有机物的正确说法是 [ ] A．聚乙烯可发生加成反应 B．石油干馏可得到

渣油气化总的反应结果是（）的反应。

A.降低温度

B.吸热热量

C.体积减小

D.体积增大

泡沫灭火器是实验室常见的灭火器材，对于电流起火的火灾也一样适用。

Water is (41) important of all the things we (42) and drink. Not many people understand this, (43) it’s quite true. The human body (人体) can go (44) food for a long time, but two (45) three days without water can usually (46) people die.
Many people don’ t understand how much water the human body needs to work well and many people do not drink (47) , even (48) hot weather.
Our body is (49) water, about 65% to 75%, ff we do not have enough water, we’ll (50) tired and many will get ill. So you see, how important water is to us all.

[A] fall [B] fell[C] feel

红灯闪烁校车停在三条以上道路上，什么情况你需要停车（）。

A.行驶在相反方向

B.行驶在相同方向

C.所有方向

D.学童走在行人道路上

确诊重症肌无力除外以下哪一项（）

A.晨轻暮重

B.服用抗胆碱酯酶药物有效

C.症状的波动性

D.家族性病例多见

E.主要侵犯骨骼肌