电源屏在周围空气温度为（）的环境下应能可靠工作。
A.-40～40℃
B.-5～40℃
C.-2～40℃
D.-1～40℃
参考答案：B
—Why are you so __________, Mei Mei?
—Because of the ________news! I failed the test again!
A．frustrated;frustrated
B．frustrating; frustrating
C．frustrating; frustrated
D．frustrated; frustrating
维护抢修过程中布放光缆时，光缆的弯曲半径应不小于光缆的（）.
A.外径的15倍
B.半径的15倍
C.外径的20倍
D.半径的20倍
