($A$) The maximum voltage range is obtained when all the components are connected in series
($B$) The maximum voltage range is obtained when the two resistors and one galvanometer are connected in series, and the second galvanometer is connected in parallel to the first galvanometer
($C$) The maximum current range is obtained when all the components are connected in parallel
($D$) The maximum current range is obtained when the two galvanometers are connected in series and the combination is connected in parallel with both the resistors

Reason : $I_1 = I_2$ implies that the fields due to the current $I_1$ and $I_2$ will be balanced.

