To be part of a rational expression, we need to have a polynomial expression.
By definition, all the exponents of a polynomial expression are positive integer values (including 0).
We know that:
![√(x)=x^{(1)/(2)}](https://img.qammunity.org/2023/formulas/mathematics/college/ibuecaiomi3bx1o9fiaxcnich95r4j4jur.png)
So the last option is not a polynomial.
Answer: The last option