Answer:
(D) .
Step-by-step explanation:
The diagram is attached below:
Theorem: An exterior angle of a triangle is equal to the sum of the opposite interior angles.
The exterior angle is the angle formed by the third side and a straight line which forms a supplementary angle with the third interior angle.
In the diagram:
are opposite interior angles.
The third angle is
The angle which forms a supplementary angle with is
.
Therefore, the exterior angle of triangle ABF is .
