---May I have a cat at home, Dad?

---Yes, you can. But you must know how to ____________ a cat.

A．look after

B．look at

C．look for

D．look up

感染过程的各种表现不包括（）

A.隐性感染

B.机会性感染

C.显性感染

D.潜伏性感染

E.病原体携带状态