Wheatstone bridge is the most sensitive when all the four resistance are of the same order of magnitude.
Kirchhoff's second law represents energy conservation.
In a balanced wheatstone bridge if the cell and the galvanometer are exchanged, the null point is disturbed.
A rheostat can be used as a potential divider.
The correct option is C. In a balanced Wheatstone bridge, if the cell and the galvanometer are exchanged, the null point is not disturbed. If we interchange the position of the galvanometer and the battery, the deflection of the null point does not change as the bridge will still remain balanced.