GCD means Greatest Common Denominator, which is the greatest number that both numbers can be divided by. You can find the GCD of a set of numbers by finding the factors of each number and identifying the greatest shared factor.

Quantity A
The factors of 14 are 1, 2, 7, and 14.
The factors of 56 are 1, 2, 4, 7, 8, 14, 28, and 56.
The GCD of 14 and 56 is 14.

Quantity B
The factors of 28 are 1, 2, 4, 7, 14, and 28.
The factors of 72 are 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72.
The GCD of 28 and 72 is 4.

Since 14 > 4, Quantity A is greater.