求大师详解：only when he had handed in his exam paper,__ he had made several grammatical mistakes.
问题描述：
求大师详解：only when he had handed in his exam paper,__ he had made several grammatical mistakes.
A.would he realize
B.he realized
C.has he realized
D.did he realize
答
D.only放在句首,句子要半倒装,从时态来讲,要用过去时.
不明白的再问哟,请及时采纳,多谢!