Which force is responsible for producing a stable
nucleus by opposing the electrostatic force of
repulsion between protons?
(1) strong (3) frictional
(2) weak (4) gravitational

(1) Strong Nuclear Force

Explanation:

When protons are placed very close to each other in the space which is very small i.e. inside the nucleus then the force between them is known as Strong nuclear force.

This strong nuclear force only depends on the distance between the protons or protons and neutrons. As the distance is decreased to very small value then this force also changes to repulsion force.

While electrostatic force between the protons is very small or negligible as we compare it with nuclear force.

So here correct answer will be

(1) Strong Nuclear Force