The correct statement explaining the Pythagorean Theorem is:
If a triangle is a right triangle, then the sum of the squares of the legs is equal to the square of the hypotenuse.
This means that if \( a \) and \( b \) are the lengths of the two legs of the right triangle, and \( c \) is the length of the hypotenuse, the theorem can be stated mathematically as:
\[ a^2 + b^2 = c^2 \]