The correct answer is A. increase in plate area and decrease in distance between the plates.
Capacitance is the ability of a conductor to store an electric charge. It is measured in farads (F). The capacitance of a capacitor is directly proportional to the area of the plates and inversely proportional to the distance between the plates.
Increasing the plate area increases the amount of space available for electrons to accumulate, which increases the capacitance. Decreasing the distance between the plates decreases the distance that electrons have to travel to accumulate on the plates, which also increases the capacitance.
Option B is incorrect because increasing the plate area and distance between the plates would not increase the capacitance. The capacitance would remain the same.
Option C is incorrect because decreasing the plate area would decrease the amount of space available for electrons to accumulate, which would decrease the capacitance. The value of the applied voltage does not affect the capacitance.
Option D is incorrect because reducing the plate area and distance between the plates would decrease the amount of space available for electrons to accumulate and would also decrease the distance that electrons have to travel to accumulate on the plates. This would decrease the capacitance.