If Ranvir covers 1500 meters in a swimming competition, then in which of the following events Ranvir is participating?

The correct option is Free style.

In competitive swimming, standard pool events are categorized by both the stroke style and the distance of the race. The primary strokes governed by international swimming regulations (such as World Aquatics, formerly FINA) include Freestyle, Butterfly, Breaststroke, and Backstroke.

The distance of 1500 meters is a prestigious, long-distance endurance event. Under standard competitive rules, the 1500-meter individual race is exclusively held as a Freestyle event (often referred to as the 1500m Freestyle).
In contrast, individual races for the other three strokes—Butterfly, Breaststroke, and Backstroke—are capped at a maximum distance of 200 meters in standard international pool competitions.

Therefore, since Ranvir is competing in a 1500-meter swimming event, he must be participating in the Free style event.