angle BAC = angle EAD (vertically opposite angles)
angle EBC = angle CDE (formed by the same arc CE)
Since 2 corresponding angles of the triangles CAB and DAE are congruent, that means the 2 triangles are similar. Hence, their sides will be in proportion.
DE/BC = AD/BA
DE/6 = 6/4
DE = 9
The correct answer is D.













