Are Mutations in the Coding Regions of DNA Primarily Favored

Multiple Choice

Are mutations in the coding regions of DNA primarily favored or selected against?

A) They are always selected for because they always increase fitness.
B) They are often selected against because they often make the mutated organism less fit.
C) They are generally maintained at a level of 50% throughout a population.
D) Selection does not act on this part of the genome.