With respect to x, what is the degree of 9y^4 - 3y^2 + 10?

Correct answer: 0

The governing concept is that degree depends on the variable named in the question, not automatically on every variable appearing in the expression. The question asks for the degree with respect to x. In 9y^4 - 3y^2 + 10, there is no x anywhere, so every term is constant when viewed as a polynomial in x. The expression is therefore an x-polynomial equal to a non-zero constant, and its degree is 0. Option C is correct. Option A is the degree with respect to y, because y^4 is the highest non-zero power of y. Option B incorrectly selects the lower y-power, and option D is unsuitable because the expression is defined and has a valid constant-polynomial degree in x.