In a circuit, a battery is used to
conduct current
slow down current
raise the potential of electrons
convert electrical energy to some other form of energy

Option (b) is the correct answer.

Explanation:

When we use a battery in a circuit then it provides voltage to the circuit. As a result there will be change in potential of electrons.

That is, when battery was not attached to the circuit then there was no potential of electrons.  But after the battery is attached then electrons start to move from there place.

Hence, there will be increase in potential of electrons.