A research paper is fact and nothing but the fact. A research paper is just giving information about a topic. However, rhetorical questions are used to persuade the reader to believe or agree with something, mainly in a discursive essay; but in a research paper, you aren't persuading, you are educating.
1. Short sound
2. Long sound
3. Long sound
4 short sound
5. Long sound
The third excerpt is structured correctly.