Two key characteristics of a good scientific investigation are hypothesis and observation of whatever organism your studying.
Adenine and guanine
Thymine and cytosine
The correct answer is option D, Temporal isolation
Temporal isolation is the mechanism which prevents the mating of closely related species living in the same ecosystem. Basically the reproductive barriers prevent these species from interbreeding. Temporal isolation is a prezygotic barrier that causes “time isolation” between the breeding period of two closely related species. The difference in time could be “difference in time of day”, “ difference in season of mating”, “difference in months” and in some cases “ difference in years”.
The answer is A. are specialized. Hope this helps