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
—Mike hurt his leg while playing football yesterday.
—_____.[ ]
A. That's nothing
B. That's all right
C. Never mind
D. I'm sorry to hear that
能够保证数据可靠传输的是（）
A.UDP
B.ARP
C.TCP
D.ICMP
