Classify angles as acute, obtuse, right, or straight.

I'll solve this problem by classifying each angle as acute, obtuse, right, or straight based on the standard definitions of these angles.

First, let's recall the definitions:
- Acute angle: An angle that measures less than 90°
- Right angle: An angle that measures exactly 90°
- Obtuse angle: An angle that measures more than 90° but less than 180°
- Straight angle: An angle that measures exactly 180°

Now I'll classify each angle:

For questions 1-10 (visual angles):
I need to visually estimate each angle and classify it.

1) This appears to be an obtuse angle (greater than 90°)
2) This looks like a right angle (approximately 90°)
3) This appears to be an obtuse angle (greater than 90°)
4) This looks like an acute angle (less than 90°)
5) This appears to be an acute angle (less than 90°)
6) This looks like an obtuse angle (greater than 90°)
7) This appears to be an obtuse angle (greater than 90°)
8) This looks like a right angle (approximately 90°)
9) This appears to be an acute angle (less than 90°)
10) This looks like an acute angle (less than 90°)

For questions 11-20 (angles with degree measurements):

11) 84° - Acute (less than 90°)
12) 89° - Acute (less than 90°)
13) 25° - Acute (less than 90°)
14) 50° - Acute (less than 90°)
15) 180° - Straight (exactly 180°)
16) 166° - Obtuse (greater than 90° but less than 180°)
17) 90° - Right (exactly 90°)
18) 125° - Obtuse (greater than 90° but less than 180°)
19) 149° - Obtuse (greater than 90° but less than 180°)
20) 106° - Obtuse (greater than 90° but less than 180°)

Here's my complete answer:

1) Obtuse
2) Right
3) Obtuse
4) Acute
5) Acute
6) Obtuse
7) Obtuse
8) Right
9) Acute
10) Acute
11) Acute
12) Acute
13) Acute
14) Acute
15) Straight
16) Obtuse
17) Right
18) Obtuse
19) Obtuse
20) Obtuse