问题
选择题
Only when he arrived home _____ that he had left his key in the office.
A．will he realize
B．he did realize
C．did he realize
D．should he realize
答案
答案：C
only+状语主句采用部分倒装，本题叙述的是过去的事情所以应该用一般过去时态答案为D。
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