Correct option is D
Given:
Total number of students = 73
Gita is 16th from the left end
Sunita is 21st to the right of Gita
We are to find Sunita’s position from the right end
Logic:
First, find Sunita’s position from the left:
Gita is at 16th
Sunita is 21 positions to the right of Gita
=> Sunita's position from the left end = 16 + 21 = 37th

Now, find position from the right:
Total = 73
Position from right = 73 − 37 + 1 = 37
Option D is correct.