如图所示,电源电压保持不变,R2=4R1,当开关接a点时,电压表的示数为U0,当开关接b点时,电压表的示数( )
A:小于0.25U0
B:大于0.25U0而小于U0
C:等于0.25U0
D:等于U0
How old ____ (be) your parents?