△ABC中,ABC所对的边分别为a,b,c,已知a=3,cosA=√6/3,B=A+π/2,①求b的

以下说法正确的是

A、HBV不同亚型之间没有交叉免疫，免疫后各亚型之间不能交叉保护

B、我国乙肝发病率在30～39岁有一高峰，因此，我国HBV感染者以成年为主

C、乙肝发病率有周期性起伏现象和明显的季节高峰

D、乙肝患者、HBsAg和HBeAg携带者均呈明显的家庭聚集性现象

E、乙肝主要通过粪-口途径传播

请帮忙给出正确答案和分析，谢谢！

The function of the sentence "A nice day, isnt it？" is______.

A．informative

B．phatic

C．directive

D．performative

请帮忙给出正确答案和分析，谢谢！

机体对HBV有免疫力的指标是

A.A

B.B

C.C

D.D

E.E

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Which of the following sentences is an emphatic sentence(强调句)？

A．What he means, in other words, his intentions is more annoying than his words.

B．His intentions instead of his words have annoyed me.

C．I was annoyed by his intentions rather than what he means.

D．It is what he means rather than what he says that annoys me.

请帮忙给出正确答案和分析，谢谢！

传染性强的指标（俗称大三阳）是

A.A

B.B

C.C

D.D

E.E

请帮忙给出正确答案和分析，谢谢！