For this case, the first thing to do is write the Pythagorean theorem for a rectangular triangle.
We have then:

Where,
a, b: sides of the rectangle triangle
c: hypotenuse of the triangle rectangle
Therefore, based on the definition we have to:
The sum of the square of the sides of the right triangle is equal to the square of the hypotenuse.
Answer:
c. in a right triangle, the square of the hypotenuse equals the sum of the squares of the legs