Justin and Amy are trying to prove the Triangle Angle Sum Theorem. Justin draws a triangle on a piece of paper, tears off the corners, and arranges them to form a line. Amy constructs a line through one vertex that is parallel to the opposite side and uses the Alternate Interior Angles Theorem to show that the interior angles add up to 180°. Who proved the theorem? Explain. A.) Both Amy and Justin proved the theorem. Amy used postulates and theorems, while Justin used a demonstration.

B.) Only Justin proved the theorem because he demonstrated that the angles formed a line.

C.) Neither Amy nor Justin proved the theorem.

D.) Only Amy proved the theorem because she used postulates and theorems to construct a logical argument to show that the interior angles in a triangle add up to 180°.