Select the correct answer. Given: , , , and are vertices of quadrilateral . Prove: is a trapezoid. Statements Reasons 1. , , , and are vertices of quadrilateral . 1. given 2. slope of : , slope of : , slope of : , slope of : 2. definition of slope 3. ? 3. ? 4. is a trapezoid. 4. definition of a trapezoid What is step 3 to complete the proof? A. by the definition of parallel lines B. by the definition of perpendicular lines C. by the definition of perpendicular lines D. by the definition of parallel lines