Answer: Option (b) is the correct answer.
Step-by-step explanation:
An atom consists of three sub-atomic particles, that is, there are protons, neutrons, and electrons in an atom.
Protons are positively charged, neutrons have no charge and electrons have a negative charge.
It is known that opposite charges attract each other. And a salt contains atoms of two or more different elements.
Therefore, there occurs attraction between a proton and an electron which is responsible for the force of attraction between the particles in a salt crystal.