Answer:
C. The mutation will become more common in offspring and increase the genetic variability in the gene pool.
Step-by-step explanation:
The mutation which is beneficial to the organism's fitness occurs in the genetic cell of the individuals and after the fusion with the opposite gametic cell during fertilization it passes to the offsprings.
So these offsprings reproduce the mutation will pass to some more offsprings and like this mutation will become more common in the population which will result in increasing the genetic variability of the in the gene pool. So the correct answer is C.