A brief taxonomy of why people raise their hands in class

During my time at UVic, I have observed a recurring phenomenon: students raising their hands in class. It seems of the utmost importance that there is an established taxonomy of the phenomenon and the reasons for it. Below is my record of humble observations.

1. Just to say, “I don’t get it.”
3. To scratch their face.
4. To participate in a poll.
5. To wave to someone else.
6. To bring up something they think is funny.
7. To confirm what the professor just said.
8. To bring up a personal example relevant for the person to what the professor just said.
9. To bring up another personal example.
10. To reply to the professor’s question because they know the answer.
11. To reply to the professor’s question because no one else will.
12. To ask a question relating to a non-class reading or a reading for a different class, which the professor knows the answer to, but which no one else in the class understands.
13. To deliver an unsolicited response to something another person said.
14. To raise what they think is a trump card on the professor, only to be destroyed by the professor in front of the class.
15. To talk without reaching a conclusion or clear purpose, after which the professor will ultimately end up confused.
16. To ask a question.