单选题 It was only after he had read the papers________ Mr. Gross realized the task before him was extremely difficult to complete.

A、 when
B、 that
C、 which
D、 what

【正确答案】 B

【答案解析】【解析】考查强调句。题干可还原为：Mr. Gross realized the task before him was extremely difficult to complete only after he had read the papers，即可判断为强调句，因此填that。