题目

My friend showed me round the town,       was very kind of him.    A. which         B. that         C. where        D. it 答案：Ａ 解析: 先行词为前面整个句子，My friend showed me round the town 。故用引导词which 。在制取蒸馏水时，常在水中放入几粒沸石(碎瓷片)，其作用是________ ____________________________________________________________．