What is an ion?

An ion may be an atom or molecule or even a particle that has some electrical charge on it. The charge on an ion may be positive or negative.

An ion is an atom or molecule with a net positive or negative electrical charge that has gained or lost one or more of its valence electrons. In other words, a chemical species has an imbalance in the number of protons (positively charged particles) and electrons (negatively charged particles).

Some examples are ${\mathrm{Al}}^{3+}, {\mathrm{Na}}^{+}, {\mathrm{Cl}}^{-}$ etc.

Hence option (A) is correct.