A student wrote a proof about the product of two rational numbers:
1. Let z = and let y = . where a and c are defined to be integers, and b and d are nonzero
integers.
2. By substitution, ry = d
3. By applying the closure property of integers and nonzero integers on multiplication, ac is an integer and bd is a nonzero integer.

What conclusion can the student now make about the product zy?

A. The product zy is rational because it can be written as the quotient of an integer and a nonzero integer.
B. The product zy cannot be an integer because bd is a nonzero integer.
C. The product zy is a nonzero integer because nonzero integers are closed on division.
D. The product zy may be either rational or irrational because the values of a, b, c, and d are unknown.