Tina correctly calculates the value of x in the diagram using the steps shown.



Step 1: y=180−104
Step 2: x=360−102−38−(180−104)
Step 3: x=144
For which reason is the equation in step 2 true?

A.
The sum of the measures of the angles in a quadrilateral is 360°.


B.
The measure of an angle exterior to an interior angle in a quadrilateral is equal to the sum of the measures of the other interior angles.


C.
The sum of the angle measures x and y is equal to the sum of the measures of the other two angles in the quadrilateral.


D.
The angles with measures y and 104° are supplementary.