Select the correct answer from each drop-down menu. The center of the circle is at O. Segment AB is tangent...

Select the correct answer from each drop-down menu.
The center of the circle is at O. Segment AB is tangent to circle O at point D.
The measure of ∠ADO is 90°.
The measure of ______ equal to 1/2 (m∠CF + m∠DE).