Physics MC Question

First of all, the circuit can be redrawn as follows:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/April07/Current1.jpg

Where k is the fraction of the resistance values of the rheostat distributed among the sides of the pointer (0 ≦ k ≦ 1)
Using the potential divider theorem, we can derive the voltmeter reading in terms of k as follows:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/April07/Current2.jpg

So voltage increases as the pointer slides from X to Y.
Then by Ohm's law, we can obtain the expression of current as follows:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/April07/Current3.jpg

Again, current increases as the pointer slides from X to Y.
Therefore the answer is A.

When move toward to y, the resistance of rheostat is increased.

The rheostat is connected parallel to resistor R.
a = resistant of resistor R
b = resistant of rheostat
c = resultant resistant

1/c = 1/a + 1/b
if b is increased, c is also increased.

V=IR
V is constant for the whole circuit.

R of whole circuit is increased, I is decreased, reading of ameter is decreased.
R at the part of voltmeter is increased, voltage dropped is also increased, reading of voltmeter is increased.