The police were looking into the accident, hoping to find out _______ that had caused it.[      ]

A. what it was

B. what was it

C. how it was

D. how was it

选择适当的试剂和物质分离的方法，除去括号中的杂质：

（1）甲烷（乙烯） 所用试剂__________， 方法_______________。

（2）乙酸乙酯（乙酸）所用试剂__________， 方法________________。