Shanghai lies _______ the east of China and _______ the northeast of Guangdong.
A:in; to
B:in; in
C:to; to
D:to; in
如图所示的电路中,电源电压恒为6V,R 为10Ω,滑动变阻器R0最大电阻为50Ω,当滑动变阻器的滑片P 由a端滑到b端,电压表示数的变化是 ()