Gladiator : Arena
Gladiator fights in Arena. i.e. X(person) shows his talent at Y(place).
- dancer : stage Dancer dances on the Stage.
- commuter : train Commuter travels in train or Traveller travels in Train. (commuter means traveller)
- teacher : classroom Teacher teaches in Classroom.
- lawyer : courtroom Lawyer practices law in courtroom.
Now if you notice option B, Train is not a place where as in all the other options we have a place (Arena, stage, Classroom, courtroom.) So option B is eliminated.
So, options $A,C$ and $D$ are left and we need to pick the best among these. i.e. a dancer, a lawyer or a teacher.
Among these the best option is Option D. lawyer : courtroom because we can relate a Gladiator with the Lawyer
The Gladiator fights in the Arena to win battles, similarly a lawyer fights in the court to win cases.
$\therefore$ Option D. lawyer : courtroom is the most appropriate choice.