The old farmer,________ the badly-injured and wounded soldier, came out of the burning house, ________for help.

A．supporting; calling

B．supported by; called

C．being supported by; called

D．being supporting; called

如图4－10为各烧杯中通电后，观察到Cu溶解，下列说法正确的是(   )

A．a是正极

B．a是负极

C．Pt极上产生气体的物质的量是Fe极的2倍

D．Q池CuSO₄溶液溶质的质量分数不变

图4－10