Question

A scientist experiments on two different pairs of objects. During the experiment, the objects in one of the pairs are brought into contact with each other; the objects in the other pair are brought close together, but they do not touch. The scientist then compares the number of electrons in each object, as recorded in the following.

Object A- is the same
Object B- is the same
Object C- increases
Object D- decreases

which pair of objects could have been charaged by friction and which pair could have been charged by induction? Please explain.