option C.
Mutations are essential for evolution to occur because they produce variations within a population.
Explanation:
This is because Mutation refer to change in the genetic content or DNA composition of organisms. Therefore , for evolution to occur there must be Mutation because it is the main source of genetic variation or causes genetic variation needed for evolution.
Mutation is important as the basics of evolution because it produce a new DNA sequence for a gene function, which lead to the formation of new allele.