问道英语选择

it引导的强调句结构为：
It is (/was) + 所强调的成分（主语，宾语，状语等）+ that(/who) + 分句

你所提问的是一句强调句的疑问句形式，改为强调陈述句是：
It was when he came into the room that you were reading a novel.
很明显，此句强调的是when he came into the room的时间状语。强调句多由普通陈述句转换而来的，你提问的这句也可写成 You were reading a novel when he came into the room.

再举例：
It was at Christmas that John gave Mary a handbag.
= John gave Mary a handbag at Christmas.
句子中的at Christmas也是一个时间状语。

好拗口..似乎真没有什么人这么说..
中国人出的英语题目好变态..真是日..
不过好像D选项顺口一点吧..
我也觉得A或者B没有什么语法错误..
这种题凭感觉吧..
我为楼主还在这种变态的题海中挣扎而默哀.

二楼正解