He arrives ______ than usual.
A:early
B:earlier
C:more early
D:earliest
She's not strong enough ____________ walking up mountains.
选出下列各句加线字意义解释都正确的一项( )
如图所示的电路中,电源电压不变,开关闭合后,若滑动变阻器的滑片P向右端移动,则 ( )