Best answer gets !

what is a necessary step for constructing perpendicular lines through a point off the line?

draw a line that intersects the first line at an acute angle using a straightedge.
draw a ray that intersects the first line at an acute angle using a straightedge.
draw arcs on either side of a given point on the line.
draw arcs on the given line in two places.

The given option 3 will be the correct.

Step-by-step explanation:

We must remember the process of constructing a perpendicular line from a point on a line.  

So, in this problem, we have to find the necessary first step to draw a perpendicular line through a point on a line.

The given option 3 will be the correct first step.

This is to draw arcs on either side of the given point on the line. (Answer)

Such that one arc intersects the line at a point.

i would have to say it is c.