Out of the options provided, the only statement that is correct is c. gene flow can introduce new alleles into a population. Gene flow such as the migration of organisms from one population to another will introduce new alleles into the population's gene pool. As a result, the frequencies of alleles in the population's gene pool will also be affected.
The other answers are incorrect because:
a. Genetic drift occurs only in small populations - Genetic drift can occur in large populations
b. Inbreeding increases genetic diversity - Inbreeding decreases genetic diversity