Let me begin by saying that you've posted no question and based on the text provided I'm only able to answer what I believe the task might be. I'm going to assume that you're supposed to fill in the blanks with suitable words or phrases.
Answers:
8.1 out (find out = figure out = work out = discover the science behind something, what does something mean or how does it work)
8.2 despite (you need to show contrast between the belief that coffee or showers help to sober up, and the fact that such claims have been proven to be false)
8.3 average (80 is an approximation and will differ from case to case)
8.4 does (firm regulation that is in place under any conditions and circumstances, it requires present simple)
