More than 20 people ________ in traffic accidents ________ last May.

A．died; for

B．have been dead; since

C．have died; for

D．have been dead, for

所谓沟通障碍，是指信息在传递和交换过程中，受噪音的干扰，而失真或中断。沟通障碍包括传送障碍、（）、信道障碍。

A.接受障碍

B.发送障碍

C.传递障碍

D.交换障碍