输注血小板治疗的原则，以下说法正确的是（）

A.使血小板达到能够完成生理作用的数量

B.使血小板计数>30×10⁹/L

C.使血小板计数>50×10⁹/L

D.使血小板计数达到100×10⁹/L

E.以上答案均不正确

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―He is a teacher. He teaches us math.

A．Where is he?

B．Why does he want to be a teacher?

C．What does he do?

D．How old is he?