Explanation

To find the capacity of the largest drum, we need to find the Highest Common Factor (HCF) of 15, 20, and 25.

Factors of 15: 1, 3, 5, 15

Factors of 20: 1, 2, 4, 5, 10, 20

Factors of 25: 1, 5, 25

The HCF among these numbers is 5.

The correct answer is: 5.