By the time Jack returned home from England, his son. from college.
A. graduated
B. has graduated
C. had been
D. had graduated
网友回答
A. graduated
B. has graduated
C. had been
(答案→)D. had graduated
解析：考查动词时态，By the time 截止到过去某时间为止做了某事，用过去完成时态。 A是一般过去时；B是现在完成时；C是过去完成进行时。根据句子意思“截止到Jack从英国返家，他的儿子已经大学毕业了。