—Let’s go to the concert this evening.It’s said to be excellent.

—I’d like to,but I have something to do.

—_________!It is the last time.We’ll have no chance to enjoy it.

A．What a pity

B．Not at all

C．All the best

D．Never mind

[问题4] 如果要对整个校园的无线连接进行计费，计费软件应基于IP计费还是基于用户账号计费简要解释原因。