Which algebraic expression is a polynomial with a degree of 4 ?

A polynomial can contain only variables raised to nonnegative integer powers. Choice C, 9x⁴ − x³ − x/5, has terms with powers 4, 3, and 1, so its degree is 4. Choice A includes 14/x, which has a negative exponent, and choices B and D do not meet the polynomial degree-four requirement.

AI-written and checked against the verified answer.