Which sets of numbers are closed under multiplication?

choose all answers that are correct.

a.
whole numbers

b.
natural numbers

c.
negative integers

d.
integers

Here are the answers to the given questions above. The sets of numbers that are  closed under multiplication are the following: Whole numbers, and Integers. The answers would be options A and D. Whole numbers are closed only under addition and multiplication. Integers are closed under addition, subtraction, multiplication, and division (with the exception of division by 0). Hope this answer helps.

I’m pretty sure the answer is a