保持压力比不变或保持两种气体介质的容积流量百分比不变的调节，叫做（）
A.等压力调节
B.等温调节
C.等流量调节
D.比例调节
参考答案：D
Although many of the houses in the small town ______ still in need of repair, there _____ lots of
improvement in their appearance. [ ]
A. are, has been
B. is, have been
C. is, are
D. are, was
有一额定值为5W、500Ω的线绕电阻，其额定电流为（），在使用时电压不得超过（）。
A．0.01A/5V
B．0.1A/50V
C．1A/500V
D．1A/50V
