D.
A fixed allele is homozygous within a population so D should be the correct answer.
Hope this helps!
Mutations. Definition. A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed.
Answer:
Flat strip of a land,raised bank ,or terrace bordering a river or canal
Explanation:
A path or grass strip beside a road