but if they are already prone to injuries which leads them to stretching more, it never says that this helps at all. what if its just a mental thing that makes them feel better, so how is that weakening the idea that stretching does not prevent injuries?

I thought the lessons said just because A leads to be leads to C doesn't mean that C leads to A? I thought you couldn't work backwards like that which is why I chose A. His explanation for why A was wrong did not make much sense.