PT114 · S1 · Q9 Some scientists believe that 65

This answer would be perfect if the paradox we were resolving was, "Given that the asteroid would only have killed off the herbivorous dinosaurs food source, how did it make all the dinosaurs go extinct"? This answer would be saying "asteroid leads to blocked sun, which leads to dead plants, which leads to dead herbivorous dinosaurs, which leads to dead carnivorous dinosaurs". The problem is we were told that the debris would only hang in the air for six months, which is too little time for the plants to disappear. So since we have no reason to think the plants disappear in the aftermath of this asteroid, we don't have reason to think the herbivorous dinosaurs die-off because their food source has disappeared. Thus, this answer doesn't get triggered, because it only has impact if we know that the herbivorous ones have died off.

One possible way to explain how the asteroid could cause the dinosaurs' extinction would be if all the dinosaurs in the world were gathered locally for some dinosaur Burning Man in the Yucatan. They would die from the impact itself, not from the ecological chain reactions. (There actually is another LSAT question that tells this exact story to resolve a similar dinosaur asteroid extinction paradox) But this answer says the opposite. It's saying "most dinosaurs would not have been killed by the initial strike", so we're even more confused how they went extinct, given that the secondary threat only lasted six months.

These are just specific facts about debris and temperature, but we don't know by percent the Yucatan asteroid dimmed the sun, so we can't apply the information in this answer to the paragraph.

Large enough for "many" dinosaurs to be killed ain't good enough. We know lots of local dinosaurs will get killed in the immediate blowback from the impact, but to render them extinct on a global scale, we need to kill more than just "many" of them.