I thought the same thing! There are other comments below about this too. I ended up picking A timed even though it isn't supported.

I think the key is that the passage is saying that "until the 19th century, the only way to make window glass was to ..." So in the 19th century, it was no longer the case that this was the only way to make glass and this method was likely still used in addition to other methods throughout the 19th century.

That’s how I interpreted this initially. I negated A and thought the conclusion would still stand because only a small % of the population works in these industries/support tariffs. Even if they all voted against an anti-tariff politician, it wouldn’t make a difference to the politician’s outcomes. BUT, I was conflating the group of people that work in these industries and the supporters of tariffs in answer choice A. We don’t if they are the same group or if there is any overlap. Also, the sentence “Polls show that in fact most people oppose such tariffs” led me to assume most people would vote against tariffs. Opposition to =/= vote against.

Agreed! Happy studying :)

I'm interested!

The stimulus says, “They [brown dwarfs] are identified by their mass and whether or not lithium is present in their atmosphere.” At this point we don’t know if having lithium makes a celestial object a brown dwarf or not having lithium makes a celestial object a brown dwarf.

The last line says, “A brown dwarf does not have a fully functional nuclear furnace and so its lithium cannot be consumed.” I think that sentence implies there is lithium in the atmosphere and it will remain in the atmosphere because the BD does not have a fully functional nuclear furnace. Therefore, we know in order to be classified as a brown dwarf, the celestial object needs to have lithium (BD → Lithium).

Answer Choice C is a restatement of this through the contrapositive.

Answer Choice C: If there is no lithium, then it is not a brown dwarf.

Contrapositive: If it is a brown dwarf, then it has lithium.