The given question is based on the Pythagorean Theorem, which states that for a right triangle with legs of lengths $a$ and $b$ and hypotenuse $c$, the relation $a^2 + b^2 = c^2$ holds true.

In the question, it is specified that if the sides $a$, $b$, and $c$ satisfy $a^2 + b^2 = c^2$, then $c$ must represent the hypotenuse. Thus, the correct answer is:

Hypotenuse

Would you like more details or have any further questions?

Here are some related questions:

1. What is the Pythagorean Theorem?
2. How can you identify the hypotenuse in a right triangle?
3. Why is the Pythagorean Theorem applicable only to right triangles?
4. What are some examples of Pythagorean triples?
5. How do you find the length of a missing side in a right triangle using $a^2 + b^2 = c^2$?

Tip: Remember, in any right triangle, the hypotenuse is always opposite the right angle and is the longest side.