A set of numbers is said to be COMMUTATIVE under the operation '+' if m + n = n + m, for any two numbers m and n of that set. Similarly, a set of numbers is said to be COMMUTATIVE under the operation '×' if m × n = n × m. Which of the following sets is COMMUTATIVE under the operation '-'?

A)the set of integers
B)the set of natural numbers
C)the set of rational numbers
D)none of the above