Answer:
The third triangle
Explanation:
The Exterior Angle is the angle a side of a shape and a line extended from the side next to it.
So for example, the first picture shows an exterior angle because a line was extended and it forms an angle with the triangle's side.
The second picture is still an exterior angle because the angle is formed with an extended line and the triangle's side.
The third photo shows an angle formed between a random line and the triangle's side. This is not an exterior angle because the angle is not formed with any side's extension.
The fourth photo is an exterior angle because it shows the angle being formed with an extension of a line from the triangle and a side of the triangle.
Hope this helps! Feel free to ask any questions! :)