A scientist is giving a demonstration with a Van de Graaff generator in a class about electrostatics. The scientist can detect the type of charge on the Van de Graaff generator by ____________________________________________.

A) bringing a positively charged balloon near it.
B) seeing if it picks up bits of paper from a surface.
C) touching it with a metallic rod that conducts charge.
D) testing if it attracts a neutral sphere made of plastic.