An acute angle is less than 90°, so for example you can choose angles A-F-B, C-F-D or E-F-D.
An obtuse angle is more than 90, so we can choose angle A-F-C for example: is it the sum of A-F-B (acute) and B-F-C (right), so the result is surely more than 90.
A right angle is an angle of 90°, which is B-F-C, because it is labeled as such
A straight angle is an angle of 180°, and AFE seems to be so, because A-F and F-E are two rays starting from the same point (F), and going opposite directions.
