A-

if R is increased then the value of current flowing in potential metre shouid decrease which will result in lower value of potential gradient(drop of potential per unit length)

Hence to re-establish balance point u wouid require to shift the point X to right(i.e toward"s point B)

i m giving here some more explanation

initially when the resistance was R then balance point was at X suppose AX=L since potential metre is balanced at this position which mean potential difference b\w A and X is equal to EMF of cell Q(EMF coz no current is flowing through Q hence no potential drop when potential metre is balanced)

Next suppose u increased the resistance which will result decrease in value of current in potential metre so for producing same potential drop=EMF of cell Q u hav to shift the balance point toward"s B..