PrepTest 143

Incorrect. If the dinosaurs were going extinct before the asteroid struck Earth, that means the asteroid wasn't the cause of those extinctions, which strengthens the conclusion that most dinosaurs weren't wiped out by that asteroid.

Incorrect. The stimulus does discuss the size of the crater, but it's unclear how the size of the asteroid and the force of its impact align with the effects on species, so this answer has an unclear effect on the argument.

Incorrect. While the stimulus does conclude that the asteroid wasn't responsible for the "vast majority" of dinosaur extinctions, it also states that major asteroid strikes kill "many organisms" near where it hits. So the argument establishes that dinosaurs likely died in the asteroid impact—explaining these fossils—just not enough to drive the majority of extinctions.

Incorrect. If there were no other asteroids at the same time, the author's argument still stands—the Chicxulub asteroid still couldn't have caused worldwide extinctions. If there were other asteroids and these killed most dinosaurs, the author's argument still stands, since it's about that specific asteroid ("this catastrophe") killing off most of the dinosaurs. Therefore, this answer doesn't weaken the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
The Chicxulub asteroid hitting Earth correlated with dinosaurs going extinct. But asteroids can only kill animals close to the site of impact—they haven't been shown to cause worldwide effects. Therefore, most extinctions weren't caused by this asteroid.

Answer Anticipation:
The argument starts with a correlation ("around the time"), but, interestingly, it concludes that there wasn't a causal relationship between the asteroid strike and the dinosaur extinctions around the same time. The argument, in fact, doesn't argue for any particular cause of these extinctions. So the main point of this argument is that this asteroid isn't the cause of "most of these extinctions."

Why not? The argument does concede that asteroid strikes kill "many organisms" near the strike site, it says that "little evidence" exists such a strike could affect organisms in other areas. So, according to this, the Chicxulub asteroid could kill dinosaurs near where it hit, but not elsewhere.

Well, that's assuming that most dinosaurs weren't living near the site of the asteroid strike! If most were, then the asteroid could have wiped them out, and the author of this argument is wrong. If most lived elsewhere, then the argument is much stronger. Since we're tasked with weakening the argument, let's look for an answer establishing that the majority of dinosaurs were, in fact, living near the Chicxulub crater.

Answer Explanation:
The author contends that the Chicxulub asteroid couldn't have caused the majority of dinosaur extinctions because it wouldn't have a worldwide impact, just killing organisms in the region of impact. If most of the dinosaurs were living in this region, then the asteroid could have wiped them out, thus causing most of these extinctions.

Key Takeaway:
Sometimes arguments conclude that one thing didn't cause another. When that happens, we can't look for our normal correlation/causation answers, but rather have to dig into the evidence for how the author argues against a causal relationship and address that.