It was only after he had read the papers Mr.Gross realized the task before him was extremely difficult to plete. (2013·大纲全国，30)
A. when
B. that
C. which
D. what
网友回答
A. when
(答案→)B. that
C. which
D. what
解析：B
解析 句意为：直到他读了文件之后，格罗斯先生才意识到他面临的任务很难完成。本句为强调句型，强调了时间状语only after he had read the papers。根据强调句结构“It is/was＋被强调部分＋that＋剩余部分”可知选B项。