#### Answer

a. The expression is not a rational expression.
b. The expression is a rational expression.

#### Work Step by Step

a. Remember that a rational expression consists of a polynomial over a polynomial. Polynomials also have degrees. The $\sqrt x$ does not have a degree (it has a non-integer exponent) so it is not considered a rational expression.
b. It is a rational expression because all of the terms have degrees (exponents).