—Do you think that man will come to your help?

—I really don’t know       a person like him can help me with.

A．how

B．what

C．why

D．if

在急性呼吸窘迫综合征(ARDS)发病中起主要作用的是

A．组胺

B．中性粒细胞趋化因子

C．激活的中性粒细胞

D．氧自南基

E．花生四烯酸