Final answer:
Mary's claim is false, as the product of two integers can be irrational.
Step-by-step explanation:
Mary's claim is:
C) False, because the product of two integers can be irrational.
To prove this claim is false, we can provide a counterexample. Let's consider the values of p = 1, q = 2, and n = √2. When we multiply p/q by 7/3, we get (1/2) * (7/3) = 7/6, which is a rational number.
Therefore, Mary's claim is incorrect, and we have shown that multiplying p/q (where p and q are both integers and n ≠ 0) by 7/3 does not always result in an irrational number.