Hola John

Although "concurso" and "competición" are very similar, we tend to use competición when we talk about sport events. We generally use concurso for events like TV contests or other skills such as drawing, writing, cooking... 

However, you could have used "recordar" as well as "acordarse de" in the other sentence. I will include it as a possible correct answer in the exercise.

Saludos

Inma