Answer: B. Van de Graaff generator
Explanation:
Van de Graaff generator is an electrostatic generator. It accumulates charge on a metallic dome via moving belt which creates a high electric potential.
A motor drives a pulley and insulating belt. A metal comb is given a positive voltage which draws electron from the belt.The positively charged belt moves upwards where another metal comb allows this positive charge to spread on the metallic dome.