Concept:A boxing contest is held inside a specialised square area known in the sport as a ring.
Explanation:The missing word must name the area where a boxer enters to fight.
In professional boxing, that area is always called a "ring", even though it is square in shape.
The word "stage" refers to a raised platform for performances, not boxing.
A "cage" is an enclosed space used in sports like mixed martial arts, not standard boxing.
A "podium" is a small platform for winners or speakers, not for fighting.
Therefore, the most suitable word for gap 72 is "ring".
Answer:D. ring