Why is the product of two rational numbers always rational? Select from the drop down menus to correctly complete the proof. The options are either integers or irrational numbers.

Let a/b and c/d represent two rational numbers. This means a, b, c, and d are ___ and ___. The product of the numbers is ac/bd, where bd is not 0. Because integers are not closed under , ac/bd is the ratio of two integers, making it a rational number.