Match the following columns.

Column I	Column II
a. Genetic drift	1. Change in the population's allele frequency due to chance alone
b. Natural selection	2. Difference in survival individuals
c. Gene flow	3. Immigration or emigration changes the allele frequency
d. Mutation	4. Source of the new alleles

A. a-1, b-2, c-3, d-4

B. a-1, b-2, c-4, d-3

C. a-1, b-4, c-2, d-3

D. a-4, b-2, c-1, d-3

Answer: Option A