The correct option is B.
A positive feed back refers to the amplification of a particular effect by its own influence on the process that gives rise to it. In positive feed back, the specific response that is obtained as a result of a process continue to increase as the process continues or increase, that is both the process and the effect generated increase.
DNA probably. It might be one of the latter rungs too, thymine, and 2 others I forgot
The answer is A - stores genetic information I think
