问题
选择题
Only after he had spent several nights working on the math problem _______ to wonder whether the problem was wrongly set.
A．that he began
B．did he begin
C．then he began
D．so that he began
答案
答案：B
only +状语位于句首要用部分到装。 句意：只有花费了数晚计算这道数学题之后他才开始怀疑是否问题出错了。