Match the columns:

Column-$I$	Column-$II$
$(1)$ Mutation	$(a)$ Change in population allele frequencies due to chance alone.
$(2)$ Gene flow	$(b)$ Difference in survival and reproduction.
$(3)$ Natural selection	$(c)$ Immigration,emigration change allele frequencies.
$(4)$ Genetic drift	$(d)$ Source of new alleles.

(D) $(1) - (d)$: Mutation is the process that introduces new genetic variations or alleles into a population.
$(2) - (c)$: Gene flow refers to the movement of alleles into or out of a population due to the migration (immigration or emigration) of individuals.
$(3) - (b)$: Natural selection is the process where organisms better adapted to their environment tend to survive and produce more offspring,leading to differences in survival and reproduction.
$(4) - (a)$: Genetic drift is the change in the frequency of an existing gene variant (allele) in a population due to random chance events.