流感病毒的核酸是()
A.一条完整的单负股RNA
B.分段的单股负链RNA
C.分段的双股RNA
D.完整的双股RNA
E.分段的单股正链RNA
参考答案:B
He is very tired. He should_______ [ ]
A. stop to working
B. stop working
C. to stop to work
D. stop to work
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