Question

2. Is this the reason        for his carelessness in his work? (explain)

这就是他在会上为他工作中的粗心所解释的原因？

Answer 1

2. (that/which) he explained at the meeting考查定语从句的用法。引导词在从句中充当动词

explain的逻辑宾语，因此，不可用why引导，可以用关系代词which或that ,亦可省略。