Answer:
The size and separation of the plates.
Step-by-step explanation:
We know that the capacitance of a parallel-plate capacitor is given by :

Where
A is the area of cross section of the plate
d is the separation between the plates
It is clear that the capacitance of a parallel-plate capacitor is directly proportional to the area of plate and inversely proportional to the separation between the plates. So, the capacitance of a parallel-plate capacitor can be determined by the the size and separation of the plates. Hence, the correct option is (A).