What is the legal height the player is allowed to serve from a. Above the waist B. Below the waist C. On the waist D. above the chest

Option B.

Explanation:

I guess that this refers to the Badminton rules, particularly to the position of the racket (or the head of the racket, where the "head" is the part with the net, that you use to hit the shuttle) when serving.

The head of the racket must be swung from below your waist. So the head of the racket must be below your waist before you do the service (With a part of the head is enough).

Then the correct option is B. Below the waist.

d.7.5cm is your answer

v=ir = 3x15 =45 v