Which is a perfect square

A perfect Square is a number that can be expressed as the production of two equal integers

Examples of perfect squares:

9, 9 is a perfect square because it can be expressed as a 3 * 3 (the production of two equals integers).

16, 16 is a perfect square because it can be expressed as 4 *4 (The production of two equals integers)

25, 25 is a perfect square because it can be expressed as 5 * 5 ( The product of two equal integers).

Non examples of perfect squares:

8, 8 is not a perfect square because you cannot express it as the product of two equals integers.

5, 5 is not a perfect square because you cannot express it as the product of two equals integers

7, 7 is not a perfect square because you cannot express it as the product of two equals integers

the answer is blue river