We were told whether _____ a Christmas party was still under discussion. [ ]

A. to hold

B. holding

C. hold

D. held

消防电话总机是消防电话系统的组成部分，能够与消防电话分机进行()语音通讯，具有综合控制功能、状态显示和故障监视功能。

A、单工 

B、双工 

C、单频 

D、双频