Scientists conclude that female cats tend to favor their right paws when _______ complex tasks.

A．knocking about

B．bringing in

C．holding up

D．taking on

电除尘一、二次电流正常不动，一次电压正常不动，二次电压指示摆动的原因是（）

A、二次电压表线圈螺丝松动

B、受到前电场粉尘影响

C、电压表线有裸露现象造成频繁对地放电

D、整流变内部短路