The strongest fundamental force in nature is
(a). Electromagnetic force
(b). Strong nuclear force
(c). Weak nuclear force
(d). Gravitational force

Hint: In nature there are 4 fundamental forces. Every fundamental force plays a vital importance to drive nature smoothly and knowingly or unknowingly we experience them in everyday life. A force is weak or strong that depends on the type of force it is having fundamentally.

Complete step-by-step solution -
The 4 fundamental forces are
Gravitational force
The weak force or the weak nuclear force
Strong nuclear force or the strong nuclear interaction
Electromagnetic force

Among all these 4 forces the Strong nuclear force also called strong nuclear interaction is the strongest one in comparison of the other three.
It is because it binds the fundamental particles of any matter together to form larger particles. Fundamental particles mean protons and neutrons. Quarks are made up of protons and neutrons and this strong nuclear force holds together the quarks. Strong nuclear force also binds the proton and neutrons to the nucleus of the atom. Also, a small strong force acts between protons and neutrons. As protons repel each other due to having the same charges, the strong forces also keep them together.
This strong force will operate only when the subatomic particles are extremely close to each other, which is approximately ${10^ {- 15}} $. So, like this the strongest fundamental force is nature keeps nature balanced by keeping the matter in stable form. Also, once they are within the range, massless charged bosons and gluons transmit the strong force between quarks and keep them stuck together.
So, this force binds the most fundamental particles in nature that’s why it is the strongest fundamental force.

Note: Strong nuclear force also binds the proton and neutrons to the nucleus of the atom. Also, a small strong force acts between protons and neutrons. As protons repel each other due to having the same charges, the strong forces also keep them together.