Mutations are always harmful happen when dna changes during replication cannot be acquired from the environment decrease the genetic diversity of a population

C I hope it helps...

happen when DNA changes during replication

Explanation:

Mutation refers to the change in the DNA of organisms. Mutations may occur upon exposure of individuals to certain mutagens, such as UV radiations, present in environment. Any error during DNA replication also leads to change in the DNA and mutations. Mutations add variations and increase the genetic diversity of the population. Mutations may be beneficial or harmful.

b brown mice / white sand dunes