问题描述：
-How long did you do your homework?-___________.
A.Before it struck 10.
B.Since supper time.
C.So long as i stayed up.
D.Until 10 o'clock.
AB能排除,解释下CD,都解释当然不反对
A.Before it struck 10.
B.Since supper time.
C.So long as i stayed up.
D.Until 10 o'clock.
AB能排除,解释下CD,都解释当然不反对
问题解答：
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