Hi Alexandra —
I think what may be causing the issue here is how you are interpreting the given tasks (as opposed to the argument itself) —
When we are asked to identify the flaw in an argument, we need an answer that, in some way, gives a direct description of the reasoning relationship between support and conclusion, which also explaining why that reasoning is wrong.
Answer choice F is something that, if true, would help show that the reasoning is flawed (and that’s why F would be viable as a “weaken” answer), but answer choice F is not, in and of itself, a direct description of the flaw.
I hope that makes sense and I hope that helps — MK