A. Angle bisector
B. Subtending an angle
C. Perpendicular bisector
D. Drawing a quadrilateral
I had been asked this question in an online quiz.
Question is taken from Construction of Parallel & Perpendicular Lines topic in section Geometrical Construction of Engineering Drawing
The best I can explain: For drawing a perpendicular through a point outside a given line, an arc is drawn from that point to the line intersecting at two points. Then a perpendicular bisector is drawn between those points and thus making a perpendicular through the point outside the line.