Pertaining to natural selection, this is a measure of the relative reproductive success of individuals. It can be measured by an individual's genetic contribution to the next generation compared with that of other individuals. A. natural selection B. traits C. selective pressures D. fitness

The correct answer is D. fitness

Explanation:

The ability of an organism to survive up to reproductive age and produce its offspring is called biological fitness. The fitness of any individual can be measured by the genetic contribution of that individual into the next generation.

This means that the higher the number of offspring produced by any individual higher would be its biological fitness. By averaging the fitness of population members the fitness of a population can be calculated. So fitness is the correct answer.