菌痢引起全身毒血症的主要因素是（）
A.菌群
B.内毒素
C.外毒素
D.机体免疫
E.细菌数量
参考答案：B
_____ what he can do. He might get a job tomorrow. He might stay out of work for weeks.
A．We didn’t know
B．He doesn’t know
C．There is no knowing
D．It was known that
皮下气肿常发生于（）
A．闭合性气胸
B．张力性气胸
C．自发性气胸
D．开放性气胸
E．闭合性血气胸
