In many species of Drosophila, flies of any genotype that are reared in a cold environment tend to be larger than flies of the same genotype raised in a warm environment. Is this an adaptation

It is an adaptation.

Explanation:

An adaptation is classified by the mutations seen in a creature in order to survive in a specific climate. If the fly is bigger in the colder climate, it is has adapted to withstand harsher temperatures than that of the warmer climate fly.

b. the carbon cycle ensures living things have a source of hydrogen