Answer:
a. the current will doubled.
Step-by-step explanation:
IN CASE 1:
Let , R be the resistance of resistor and it is given that the potential difference produced by battery is V.
Therefore, current through circuit is ,

Now,
IN CASE 2:
The potential difference now is doubled i.e. 2 V.
Since, resistance of a body depends on its nature.
Therefore, Temperature remains constant.
So, current through circuit is ,

Therefore, potion a) is correct.