The actual answer is "always", as adjacent angles have no common interior points under any circumstances. The correct option among all the options that are given in the question is the first option or option "A". I hope that this is the answer that you were looking for and it has come to your help.
we can divide the composite shape into on quadrilateral and triangle as shown in the diagram. since the line that joins the two shape is parallel to the base AB, the angle DEC is 85°.The angle CEA is 180°- angle DEC = 180-85=95. Angle BCE is sum of angle CEA, ABC and EAB subtracted from360°= 360°-(95+95+85)=85°. Angle DCE is 120°- ECB=35°. So, angle CDE = 180°-(35°+85°)= 60°. For reference see the diagram.
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