1.1. Anne is writing a proof about the figure shown on the coordinate plane below. She wants to show that quadrilateral ABCD is a parallelogram. I Which of these is a correct, complete plan for Anne's proof? A. Show that AB and DC have equal slopes. B. Show that AB and DC have the same length. C. Show that the midpoints of DB and AC are the same point. D. Show that DB and AC have slopes that are negative reciprocals of each other.​