1. The problem asks for the square root of 25 expressed as a surd. 2. A surd is an expression containing a root that cannot be simplified to remove the root. 3. Since 25 is a perfect square, $\sqrt{25} = 5$, which is a whole number, not a surd. 4. Therefore, the square root of 25 expressed as a surd is simply $5$ (option b). 5. The next problem asks which of the following is an example of an irrational number expressed as a surd. 6. An irrational number cannot be expressed as a simple fraction and its decimal form is non-terminating and non-repeating. 7. Surds like $\sqrt{2}$, $\sqrt{3}$, or $\sqrt{5}$ are irrational because they cannot be simplified to rational numbers. 8. So, any surd that is not a perfect square root represents an irrational number. Final answers: - Question 1: $5$ - Question 2: Any surd representing an irrational number, e.g., $\sqrt{2}$ or $\sqrt{3}$.