The following would be an example of positive eugenics

The correct answer is "encouraging athletes to have children together".
Eugenics is a term referring to the belief that the genetic quality of the human population can be improved. Two types of eugenics can be recognised: positive and negative eugenics. Positive eugenics aim to increase the reproductive rates of people with desirable traits. Negative eugenics aim to reduce the reproductive rates of people with problematic or less-desired traits and sometimes sterilize them to prevent them from having offsprings. In this example, the act of encouraging athletes to have children together consists an act of positive eugenics, because it encourages people with desirable traits to have offsprings.