i.e. Q ∝ V
Where C is the constant of proportionality called capacitance of the capacitor.
The capacitance(C) of a capacitor depends on its geometrical configuration(i.e. size and shape) of the capacitor and on the dielectric medium inside it.
e,g, Capacitance of a parallel plated capacitor, C=K ϵ0Ad
Therefore, On changing Potential difference, the charge on the capacitor changes proportionately and vice versa. But capacitance does not change, as it is the constant of proportionality.
Hence Correct answer is Option A