A:May I have three pies, please?
B:May I have three cakes, please?
如图所示电路,电源电压不变,闭合开关,当滑动变阻器R1的滑片向上移动时,以下说法正确的是( )
假如第一处错误已纠正,则第二处错误在哪里?应如何改正?