Naphthalene balls are obtained from coal tar and used as mothballs, PVC, pesticides, dyes, toilet freshener blocks and phthalic anhydride. It is the largest constituent of coal tar and is flammable. Naphthalene balls are called moth balls because toxic gas released from the naphthalene balls kills moths and other pests.
So, if you are looking for the correct answer to this question, then:
c. coal tar
Correct answer is: c. coal tar