Looking at the electroscope, describe how you can cause the two leaves at the bottom to repel each other and stay that way.
a) bring a positive and negative object near the top.
b) bring a negative object near the top.
c) bring a positive object near the top.
d) touch the electroscope with any charged object.

The electroscope functions on the presence of charge therefore to repel the two leaves away any charged object will be helpful.

Option D

Explanation:

The electroscope is a device which functions to detect the charge on the given object. When the two leaves in the electroscope are normally placed, shows no charge is present.

To repel away the leaves, presence of charge is important and therefore when a charged body touches the electroscope, by the induction of opposite charge develops in the electroscope by which the leaves gets similar charges and hence repels away.

the bal will not change its velocity.