稳压管两端电压变化量与接通它的电流变化量之比值称为稳压管的动态电阻。稳压性能好的稳压管的动态电阻（）
A.较大
B.较小
C.不定
D.固定
参考答案：B
—Did the actor live alone in his house?
—Yes. He has a wife and two children. But ______ of them live with him. [ ]
A. none
B. all
C. both
D. neither
着重考虑优势因素和威胁因素，目的是努力使优势因素影响趋于最大，用优势因素抵抗威胁因素的方法是( )方法。
A．WO对策
B．WT对策
C．ST对策
D．SO对策
