Which of the mechanisms below increases the amount of genetic variations in a population?

a. Genetic drift

b. Gene flow

c. Bottleneck effect

d. Founder effect

B, because its the matter of how many different genetic variations are there.

B is quite close, but it defines the existing variation within the population, which is positive but only goes so far if there is not new material being introduced.

C and D decrease the genetic variation of a population

So the right answer is A, because it actually results in new genes being created through mutation.