在目前的实用光纤通信系统中采用()调制方式,即将调制信号直接作用在光源上,使光源的输出功率随调制信号的变化而变化。
A.直接
B.间接
C.外
D.分接
参考答案:A
The poor man's life was ____ of the king. [ ]
A. at the mercy
B. at the call
C. at the service
D. at the expense
卷筒禁止焊修。()