A force between two protons is the same as the force between proton and neutron. The nature of the force is.
A. weak nuclear force
B. strong nuclear force
C. electrical force
D. gravitational force

Hint: Nucleus consists of protons and neutrons. If there are only protons in the nucleus there will be huge repulsion between them and the nucleus becomes unstable. Hence neutrons are also present in the nucleus. There will be force between these protons and neutrons. This is one of the fundamental forces of nature.

Complete step by step answer:
In an atom generally between protons since they are of positive charge and will be enclosed in smaller space electric repulsive force will be existing. Subatomic particles which are present inside the atom are called nucleons. So protons and neutrons are called nucleons. Irrespective of the charge present on nucleons there is always force acting between two nucleons. That is called strong nuclear force. It is one of the fundamental forces. The amount of strong nuclear force acting between two protons is the same as the amount of strong nuclear force acting between two neutrons. This force has the shortest range among all the fundamental forces. Particles should be extremely close to each other in order to have the effect of this force. This force is always attractive in nature and the main reason for the stability of the nucleus.

So, the correct answer is “Option B”.

Additional Information: In case of nuclear reactors we bombard heavy uranium atoms with fast moving neutrons to cause fission of uranium because in order to split uranium atom we need high kinetic energy for bombarding neutrons to overcome strong nuclear forces of uranium nuclei.

Note: If we consider the magnitude of force between proton and proton and magnitude of force between neutron and neutron the second one would be greater as between proton and proton repulsive force also exists which gets subtracted from strong nuclear force but in case of neutron and neutron, only strong nuclear force exists.