Concept: The question tests on the area of Combinatorics
Solution:
The number of revolutions taken by a circular surface of radius r to travel a distance d is given by n = d / 2πr
Here d = 75 yards = 75 * 3 = 225 feet
r = 2.5 feet
Assuming π = 22/7
n = 225/2∗22/7∗2.5=14.31 ≈ 14
Time taken for 1 revolution = 30 seconds
Therefore time for 15 revs = 14 * (1/2) = 7 minutes
Option D