A certain amount of charge $(q)$ is placed on the plates of a capacitor, with capacitance C $,$ to produce a potential difference of V $.$ When the charge on the plates $($which have not been moved or adjusted$)$ is increased to $3$ q :

the capacitance decreases to $\frac{C}{3}$

the potential difference across the plates increases to $3$ V

the capacitance increases to $3C$

the potential difference across the plates decreases to $\frac{V}{3}$