What are the two phases of speciation?
a. geographic isolation and variation
b. adaptation and reproductive isolation
c. adaptation and variation
d. geographic isolation and reproductive isolation

D is the right answer for this question on e2020

D. geographic isolation and reproductive isolation

Speciation can be defined as a evolutionary process by which a new species develop from a parent species. It occurs when the members of the species becomes reproductively isolated and physically get separated due to geographical barriers. In allopatric speciation, the ancestral population evolve into a new species due to geographical barriers like river which separate the two populations of the same species apart. In sympatric speciation, the ancestral population evolve into a new species due to the reproductive and behavioral isolation. This is due to the fact that the members of the two species becomes incapable of inbreeding.

the answer to your question is:

c. complementary base-pairing