问题
选择题
If you often feel tired and can't focus your attention, that is________you have to stop working too
hard and to have a rest.[ ]
A. why
B. whether
C. when
D. what
答案
答案：C
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If you often feel tired and can't focus your attention, that is________you have to stop working too
hard and to have a rest.[ ]
A. why
B. whether
C. when
D. what
答案：C
