Which expression is not a polynomial but looks like a monomial?

Correct answer: \(-5\sqrt{x}\)

In \(-5\sqrt{x}=-5x^{\frac{1}{2}}\), the exponent of \(x\) is \(\frac{1}{2}\). In a polynomial, variable exponents must be non-negative integers, so this is not a polynomial even though it appears to have just one term. In contrast, \(9x^2\), \(7x\), and \(11\) have exponents 2, 1, and 0 respectively, so they are polynomials. Exam tip: Rewrite a square root involving a variable as an exponent and check that exponent.