Final answer:
The capacitance of a capacitor does not change when charge is removed from the plates; it is determined by the physical characteristics of the capacitor and the dielectric material, not by the electric field or the amount of charge. Option A is correct.
Step-by-step explanation:
The capacitance of a capacitor does not change when charge is removed from it. The capacitance is a property that depends on the geometry of the capacitor (the area of the plates and the distance between them) and the dielectric material between the plates but not on the amount of charge on the plates or the electric field strength.
When the electric field between the plates of an air-filled capacitor is weakened by removing charge from the plates, the capacitance remains constant because none of the factors that determine capacitance (area, distance between plates, and dielectric material) have changed.
In the context of dielectrics, adding a dielectric material between the plates of a capacitor can increase its capacitance because the dielectric reduces the electric field strength inside the capacitor. This leads to a smaller voltage V for the same charge Q, and since capacitance C is calculated as C = Q/V, the capacitance increases.