Marco is an athlete and plays three different types of sports. when he sees emma in a track suit, he assumes that she is an athlete as well. the reason this happens is that marco's schema is

The correct answer to this is:

Marco’s schema is "primed by the representativeness heuristic".

In psychology, heuristics are rules or set rules which are used by people to form judgments or make decisions. Marcos associates Emma to be an athlete as well due to the track suit. In this case, the track suit represents an athlete.