Why is the product of two rational numbers always rational?

Select from the drop-down menus to correctly complete the proof.

Let a/b and c/d represent two rational numbers. This means a, b, c, and d are _____, and b and d are not 0. The product of the numbers ac/bd, where bd is not 0. Both ac and bd are _____, and bd is not 0. Because ac/bd is the ratio of two _____, the product is a rational number.

Blank 1:
a. integers
b. irrational numbers

Blank 2:
a. integers
b. irrational numbers

Blank 3:
a. integers
b. irrational numbers

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