Answer:
a. a balance beam
Explanation:
so, sports is a VERY broad topic, there's soccer, football, cricket, baseball, track, swimming, etc. so that's not a narrow topic.
Olympics is a little narrower because not ALL sports are in the Olympics, but it's still VERY broad
and gymnastics is even more narrow, but it could get more narrow, there's floor routines, and all the rest, so balance beam in THE most narrow
