Diversity among members of a species is important because diversity

Diversity usually refers to the variety of lifeforms that exist on earth. This diversity among the members of species is important because each and every organism living on earth plays a very crucial role in enhancing the productivity of the ecosystem.  

The more diversified species are better developed than they can adjust themselves in a new type of environment. The diversified species have high chances of survival and can be selected naturally in the environment.

it is either c or d and i know for sure it is not a or b

the answer is b.) hydrogen bonds between bases.