问题
选择题
He doesn't know_____ to hand in the homework. I think he may do it tomorrow.[ ]
A. where
B. what
C. which
D. when
答案
答案：D
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He doesn't know_____ to hand in the homework. I think he may do it tomorrow.[ ]
A. where
B. what
C. which
D. when
答案：D
8Fe +nCO2+2nH2O，其中n的值为____________（填数字）。