Answer:
A. C. E. F.
That is, 2, 3, 5 and 6.
Explanation:
In geometry, exterior angles are any angle place between any side of a shape and a line extended from the next side, as the figure shows.
As you can see, angle 2 and 3 are formed by a side of the triangle and an extended line from the next side. Similarly, angles 5 and 6 are formed the same way. Therefore, those four are exterior angles.