问题
选择题
By the time Jack returned home from England, his son __________from college.
A．graduated
B．has graduated
C．had been graduating
D．had graduated
答案
答案：D
本题考查动词时态。句意为“当杰克从英国返回家时，他的儿子已经大学毕业了。”by the time到…时候为止，一般与完成时连用。选D。