Final answer:
If you multiply the polynomials (x - 1) and (x + 1), you get the function x^2 - 1 which is not a polynomial. The statement that is not always true is option C: If f(x) and g(x) are polynomials, then the product is a polynomial.
Step-by-step explanation:
The statement that is not always true is option C: If f(x) and g(x) are polynomials, then the product is a polynomial.
This statement is not always true because the product of two polynomials may result in a non-polynomial function. For example, if you multiply the polynomials (x - 1) and (x + 1), you get the function x^2 - 1 which is not a polynomial.
Therefore, option C is the correct answer.