高频开关电源由于工作频率（），所以变压器和滤波元件的体积和重量（）。
参考答案：高；小而轻
Because it was hard to _____ with the money he got paid, he wanted to take ____ job.
A．make his life; a second
B．make ends meet; a second
C．earn his living; the second
D．make his living; the second
某一容器释放气体，已知分子量M=86，设计温度t设=135℃，背压对释放能力修正系数Kb=1，安全阀整定压力Ps=0.4MPa，气体释放量Wv=2770kg/h。则在选用安全阀时，安全阀喷嘴喉部直径do应不小于( )。
A．(3.2cm
B．(3.02cm
C．(2.59cm
D．(2.89cm
