Answer:
C.an exterior angle
Step-by-step explanation:
Definitions:
Remote interior angle : The two angles inside the triangle that do not share a vertex with the exterior angle.
Adjacent interior angle : An adjacent interior angle to the exterior angle is the angle that together with this exterior angle are supplementary
An exterior angle : The angle between any side of a shape, and a line extended from the next side.
Complementary angles : Two Angles are Complementary when they add up to 90 degrees.
So, when we extend any side of the triangle so the angle formed with thus extended line satisfy the definition of exterior angle
Thus new angle is created by extending one side of a triangle is exterior angle
Hence Option C is correct