I have to choose one as the greatest of the 4 forces.

gravity - weakest
weak force - no

so it would have to be strong force or electromagnetic force

2 answers

The strong force is the strongest. The Weak force is not really weak, it is as strong as the electromagnetic force. However, the weak force decays exponentially as a function of distance.
which one opf the 4 forces opposes the electromagnetic force in the nucleus of an atom:

strong force
weak force
gravity

I thought it was stong force