Be careful when you cross this very busy street.If not ,you may _____run over by a car .  

A．have

B．get

C．become

D．turn

静脉输注即时半衰期（context-sensitivehalf-time）最稳定的是（）

A.吗啡

B.芬太尼

C.阿芬太尼

D.舒芬太尼

E.瑞芬太尼