ATM为异步传输模式，但本质上仍是一种( )传输模式。
A．报文
B．分组
C．线路
D．都不是
参考答案：B
( )是收集一手资料时最普遍采用的手段。
A．问卷
B．座谈
C．电话
D．邮寄
My sister met him at the Grand Theatre yesterdays afternoon, so he ________ your lecture.[ ]
A. couldn't have attended
B. needn't have attended
C. mustn't have attended
D. shouldn't have attended
