造成地球上海陆变迁的主要原因是( )
如图所示的电路中,电源电压保持不变,R1=10Ω,R2=20Ω,R3的阻值不为零,当开关S1闭合,S2断开时,电压表的示数为8V;当开关S1、S2都闭合时,电压表的示数可能值为( )
A. Leo took the drawing lesson.
B. He likes the colours.
C. I like the one on the left.
D. She likes the horses. The horses look powerful.