The correct answer is option 1, which states that a stable nucleus with a low mass number (A < 10) has exactly the same number of neutrons and protons.

To understand this, let`s first define what protons and neutrons are. Protons are positively charged particles found in the nucleus of an atom, while neutrons have no charge and also reside in the nucleus. Both protons and neutrons are collectively known as nucleons.

For a nucleus to be stable, it needs to have the right balance between the forces of attraction and repulsion among its nucleons. This balance is achieved when the number of protons and neutrons is approximately equal.

Option 2 is incorrect because having more neutrons than protons would result in an unstable nucleus. The excess neutrons would lead to a stronger repulsive force, causing the nucleus to become unstable and undergo radioactive decay.

Option 3 is also incorrect because having no neutrons would result in a nucleus that is composed of only protons. However, without the presence of neutrons to help overcome the electrostatic repulsion between protons, the nucleus would become unstable.

Option 4 is incorrect because having no protons would mean the nucleus is made up entirely of neutrons. This type