A:the 1980s; his twentie
B:the 1980s; the twentie
C:the 1980s; twentie
D:1980s; the twentie
89____100 80+8____90-2
如图所示电路中,电源电压保持不变,当开关S闭合,滑动变阻器的滑片P向右滑动时,电压表示数的变化情况是 ( )