Answer:
From each intersection point, draw an arc above side EF so that the two arcs cross.
Explanation:
In the image attached, the two arcs crossing represent the demonstration of segment AD as perpendicular.
Therefore, the right answer is the third choice.
First, we have to draw to arcs across the line that create two points.
Then, from those points, we draw two intersecting arcs.
At the ends, we draw a line intercepting the two intersecting arcs.
That's why choice C is the right answer.