How can you tell if a triangle is a right triangle with one 90 degree angle?

A. You would have to know two of the angles or all three sides to test the Pythagorean theorem.
B. Look and see if the triangle looks like it has two perpendicular sides.
C. Draw the triangle and use a protractor to measure the length of the sides and angles.
D. Plot the triangle on the coordinate plane and use the coordinates to see if the triangle is a right triangle.

A. You would have to know two of the angles or all three sides to test the Pythagorean theorem.