由于正处于某种疾病的潜伏期或者前驱期，恰巧接种疫苗后发病属于（） A.一般反应 B.

用所给词的适当形式填空。

       What do you think of watching TV? I don't think it is good for students. First, children       1        (be) different from adults. It's true that students like       2       (relax) by watching TV. However, the dangerous thing is that they can't take their eyes off the screen. They will go on watching TV for hours and hours. It's bad for their eyes.      3      (two), many students have the habit of     4     (watch) too much TV. Then they will have little time for sports. Third, some TV programs are not     5    (suit) for students. Some even lead them to comes, which I think is a terrible thing.

一个角的余角与这个角的3 倍互补，求这个角的度数．

水蒸气蒸馏法主要用于提取（）

A.强心苷

B.黄酮苷

C.生物碱

D.糖

E.挥发油

基坑边缘堆置土方和建筑材料．或沿挖方边缘移动运输工具和机械，一般应距基坑上部边缘不少于（）。

A．2m

B．2.5m

C．3m

D．3.5m

当今世界，国家之间和地区之间的竞争，实质上是（）的竞争，这个竞争的核心是自主创新能力的竞争。

A.经济

B.政治

C.科技

D.文化