I think what got me here was my misunderstanding of the underlying "rules" of the question.

A felt like a cheap "well what if I just made up this new fact that totally contradicts all your facts?" kind of answer, which I think I subconsciously assumed wasn't how we are supposed to approach these types of questions.

If A had been written more like "the argument fails to consider that smokers may be less likely to develop heart disease..." I think I would have got it immediately, but the way it was written like this factual claim that we just made up threw me through a loop.

#feedback: Questions like #3 actively throw me off what would otherwise be a solid learning course. I'm getting the impression that it's meant to show an outlier to the rules for necessary condition signifiers, but I'd rather you just let me learn the basic rules before throwing outlier examples at me.

As it's set up now, I feel like #3 contradicts what the course taught me, making me less likely to rely on necessary signifiers as a whole moving forward. It doesn't help that the video explanation makes no mention at all of the obvious contradiction.

I also got tripped up between A and B. I can see why A is wrong. We can't assume that methods used "until the 19th century" were in use specifically in the 17th century.

I disagree with the video's explanation that the "Later" methods can be reasonably assumed to refer to the 19th century.

I think this is one of those questions where you have to choose the answer that is least wrong.

Can someone clearly explain to me why we know not to treat traffic congestion decreasing as another required condition for profits to increase? I've reviewed the negate sufficient lesson and it is just not clicking.

Every explanation I can find makes it seem like it should be obvious, but I'm clearly not getting something. I understand why B is the correct answer when broken down into a logic equation, but I don't understand, on a conceptual level, why we know not to treat traffic congestion decreasing as a second condition to increased profit.