Which one of the following is a primary consideration in determining the capacitance of a parallel-plate capacitor?
a) the size and separation of the plates
b) the potential difference across the plates
c) the shape of the plates
d) the particular materials used to fabricate the plates

The size and separation of the plates.

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).