The relationship between charges can be described by saying,

a.) charges do not interact.
b.) negative charges attract.
c.) neutral charges repel.
d.) opposite charges attract.

The correct answer for above statement is:

d.) opposite charges attract.

Explanation:

Electric charges are of two generic types: positive and negative. Two objects that have an abundance of one type of charge exercise a force of repellency on each other when comparatively close together. Two objects that have excess opposite charges, one positively charged and the other negatively charged, bring each other when approximately near.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue