so many houses have burglar alarms nowadays.it is a()of the time._英语解答

so many houses have burglar alarms nowadays.it is a()of the time.A sign B signal
AB那个正确为什么

人气：143 ℃　时间：2020-06-08 04:25:56

解答

a 是正确的
a是标志象征
b是信号的意思多指电子信号