在各种化学性致癌物中致癌谱广,致癌力又强的是()
A.烷化剂
B.亚硝胺类
C.霉菌毒素
D.芳香胺类
E.氨基偶氮类
参考答案:B
“南澳一号”考古中,潜水员携带压缩空气瓶进行水下探宝。空气可被压缩说明[ ]
A.分子由原子构成
B.加压时发生化学变化,产生更多氧气
C.分子体积很小
D.分子间有间隔
用括号内所给单词的适当形式填空。
1. Thomas Edison was a great American (invent).
2. We have (fly) on the plane for two hours.
3. You must keep the child away from the (boil) water. It is dangerous.
4. I want to play on China s (nation) basketball team some day.
5. I think it's very uncomfortable to wear high (heel) every day.