What is the area of the triangle in the diagram?

12(x21+y21)(x22+y22)−−−−−−−−−−−−−−−−√

1/2(x22−x21)(y22−y21)−−−−−−−−−−−−−−−−√

(x21+y21)(x22+y22)−−−−−−−−−−−−−−−−√

2(x22−x21)(y22−y21)−−−−−−−−−−−−−−−−√

Question

What is the area of the triangle in the diagram?

12(x21+y21)(x22+y22)−−−−−−−−−−−−−−−−√

1/2(x22−x21)(y22−y21)−−−−−−−−−−−−−−−−√

(x21+y21)(x22+y22)−−−−−−−−−−−−−−−−√

2(x22−x21)(y22−y21)−−−−−−−−−−−−−−−−√

anonymous · Answer

attachment

anonymous · Answer

@bohotness

anonymous · Answer

It was not B
Another sources said it wasn't C either. 
50/50 now Good luck Plato Friends.

anonymous · Answer

It was A.
Stay strong Plato members and move on.