对于停等流量控制，为了发送n个数据包，需要（）个确认帧。
A.n
B.2n
C.n-1
D.n+1
参考答案：D
—I think we should give a hand to the elderly when they fall onto the ground.
— ___________. Everyone needs help when they are in trouble.
A．Sorry, I can’t
B．Never mind
C． I don’t agree
D．I agree
在导游服务中，导游员可有原则的讨好游客，投其所好，满足其“优待需求”。()
A．正确
B．错误
