Question

CF is a straight line.

Answer 1

Step-by-step explanation:

When you move point A horizontally to the right or left, the measures of angles ADC and ADE change, but the sum of their measures is always 180° since angles ADC and ADE are a linear pair and are supplementary, so the sum of their measures is 180°.

The same is true of point B moving horizontally and the measures of angles BEF and BED.