He told us that the moon _____ very far from the earth. [ ]
A. was
B. are
C. were
D. is
答案:D
氧化还原反应的本质是 [ ]
A、氧元素的得失
B、化合价的升降
C、电子的转移
D、分子中原子的重新组合
下列物质中,能引起环氧乙烷聚合的是()。
A、铁
B、石棉
C、橡胶
D、水