正常停炉后（）小时，可在检修的要求下启风机进行通风。
A、4
B、6
C、10
D、18
参考答案：D
某宽带直放站的工作频点号为F1、F2，则其下行三阶互调产物的频率为（）。
The sense of mistrust is compounded by smaller annoyances that leave the families feeling as though no one in authority cares about them.
A．offset
B．intensified
C．diminished
D．annulled
