问题
选择题
I am ashamed, sir, that I wasted the many hours __________ I should have studied in class.
A．while
B．before
C．which
D．when
答案
答案：D
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I am ashamed, sir, that I wasted the many hours __________ I should have studied in class.
A．while
B．before
C．which
D．when
答案：D