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 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.

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