题目内容
Radioactivity is dangerous. It may cause skin burns, it may destroy good tissues（组织）and it may cause illness that could be passed on to our children and. grand children. In case of exposure（暴露）it may even cause death.
In the early days of radioactivity, scientists did not realize these dangers. Marie and Pierre Curie, after having worked for a while with radioactive materials, noticed that their fingers were reddened and swollen（红肿）and the skin was peeling off. Henry Becquerel carried a small tube with radium in it in his waistcoat pocket, and was surprised to find a bum on his chest. Other early workers also reported bums and harm of different kinds.
The strange fact is that it can harm without causing pain, which is the warning signal we expect from harmfulness. Pain makes us pull back our hands from a fire or a hot object, but a per-son carrying radioactive materials has no way of telling whether he is touching something too“hot” for safety. Besides, the“burns” or other harmfulness that radioactivity produces may not appear for weeks. A person may have been hurt without knowing it for some time.
(1) Which is the topic sentence for this passage?
[ ]
A．Radioactivity may ever cause death.
B．Radioactivity does great harm to children.
C．Radioactivity may do harm to people without being known.
D．Radioactivity is dangerous.
(2) A few people were mentioned in the passage. They ________.
[ ]
A．were all famous scientists of great achievements
B．died of radioactivity
C．knew little about radioactivity
D．did experiments on themselves to find the danger of radioactivity
(3) According to the point of the passage, pain ________.
[ ]
(4) The sentence in the fifth line of the second paragraph“the skin was peeling off”means“________”．
[ ]
解析：
