What is the best next step in the construction of a line that passes through b and is perpendicular to line a?

a. set the compass to be equal to cd
b. set the co pass to be wider than it was when placed at point b to draw the arc that passes through c and d
c. set the compass to be greater than cd
d. keep the compass setting the same width as when it was placed at point b to draw the arc that passes through c and d