Answer:
The correct option is : A. the most reproductively successful in an environment.
Step-by-step explanation:
The phrase ''survival of the fittest" originated from the evolution theory given by Darwin. In the Darwin's theory of Evolution, this phrase was used to describe the process of natural selection, which defines the concept of fitness as the reproductive success. Therefore according to this theory, the species which will leave the most copies of itself in the successive generations will survive.
Therefore, the term “survival of the fittest” refers to the most reproductively successful in an environment.