Answer: D. Definition of Supplementary Angles
Explanations:
Note from the diagram shown that:
AMB forms a straight line
This means that < AMB = 180 degrees (Because sum of angles on a straight line is 180 degrees)
Also note that the sum of angles on a straight line is 180 degrees
< AMC + < CMD + < DMB = 180 (sum of angles on a straight line)
Since < AMB = 180
< AMC + < CMD + < DMB = < AMB
Since the above indicates that the sum of the angles add up to 180 degrees, they are supplementary angles.
Note that supplementary angles are angles that add up to 180 degrees