Task 4 Directions: The following is a list of terms. After reading it, you are required to find the items equivalent to those given in Chinese in the table below. Than you should put the corresponding letters in the brackets of question NO. 51-55. A--abbreviated dialing code B--off-peak hours C--charging period D--access code E--identity number F--video conference G--operational status H--information subscription service I --Network User Address J --audio signal K--local user terminal L--file management M--response signal N--operating instructions O--change of the battery unit P--function indicator Q--entry rejected R--external control 51．( )计费时间 ( )非高峰时间 52．( )网络用户地址 ( )标识码 53．( )本地用户终端 ( )音频信号 54．( )文件管理 ( )操作指令 55．( )外部控制 ( )功能指示