By the time Jack returned home from England, his son from college. A．graduated B
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By the time Jack returned home from England, his son ________ from college.
A．graduated
B．has graduated
C．had been graduating
D．had graduated
试题答案
D
解析：by the time引导时间状语时，若从句用一般过去时态，则主句要用过去完成时态。句意：当杰克从英格兰回到家里的时候，他的儿子已经大学毕业。故只有D项符合题意。