--- My mother has a cold today, and I have to take care of her.

---            .

A．Thank you

B．Oh, I don’t know

C．I’m sorry to hear that

D．That’s Ok.

小儿肺炎最主要的发病机制是

A．缺氧

B．酸中毒

C．毒血症

D．水钠潴留

E．二氧化碳潴留