Katie is constructing the circumscribed circle for △RST. She has already used her compass and straightedge to complete the part of the construction shown in the figure.



What could be her next step?


Use the straightedge to draw the line through points A and C.

Use the straightedge to draw the line through points C and D.

Use the straightedge to draw the line through points C and B.

Use the straightedge to draw the line through points B and D.