Selena: Asteroid impact on the Earth caused the extinction of the dino

Question

Selena: Asteroid impact on the Earth caused the extinction of the dinosaurs by raising vast clouds of dust, thus blocking the Sun's rays and cooling the planet beyond the capacity of the dinosaurs, or perhaps the vegetation that supported them, to adapt. A worldwide dust layer provides evidence of asteroid impact at approximately the correct time, and a huge crater exists on the edge of the Yucatán peninsula in Mexico.

Trent: That asteroid crater is not large enough for the requisite amount of dust to have been produced. Besides, the extinction of dinosaur species took many years, not just one or two. So the extinctions must have been due not to asteroid impact on the Earth but to some other kind of cause.

Trent's argument assumes that

(A) any collision of an asteroid with the Earth would have occurred on a land area rather than an ocean

(B) dinosaurs in the neighborhood of an asteroid impact but not within the zone of direct impact would have survived such an impact

(C) any event that takes place over a long period of time has many different kinds of causes

(D) dust from the impact of an asteroid on the Earth would not have had any cooling effect on the climate

(E) no more than one large asteroid struck the Earth during the period when the dinosaurs were becoming extinct

guddo · Accepted Answer

Selena: Asteroid impact on the Earth caused the extinction of the dinosaurs by raising vast clouds of dust, thus blocking the Sun's rays and cooling the planet beyond the capacity of the dinosaurs, or perhaps the vegetation that supported them, to adapt. A worldwide dust layer provides evidence of asteroid impact at approximately the correct time, and a huge crater exists on the edge of the Yucatán peninsula in Mexico.
 
 Trent: That asteroid crater is not large enough for the requisite amount of dust to have been produced. Besides, the extinction of dinosaur species took many years, not just one or two. So the extinctions must have been due not to asteroid impact on the Earth but to some other kind of cause.
 
 Trent's argument assumes that

Trent argues that the known asteroid impact could not explain the extinction because the crater was too small and the extinction occurred over many years.  The key assumption  is that  there were not several large asteroid impacts during that period . Otherwise, multiple impacts could still explain both the amount of dust and the long extinction period.

(A) any collision of an asteroid with the Earth would have occurred on a land area rather than an ocean

Incorrect. Trent does not need to assume where an asteroid would have struck.

(B) dinosaurs in the neighborhood of an asteroid impact but not within the zone of direct impact would have survived such an impact

Incorrect. Trent's argument is about dust and climate effects, not survival near the impact site.

(C) any event that takes place over a long period of time has many different kinds of causes

Incorrect. Trent does not claim that every long event must have multiple kinds of causes.

(D) dust from the impact of an asteroid on the Earth would not have had any cooling effect on the climate

Incorrect. Trent questions whether enough dust was produced, not whether dust could cool the climate.

(E) no more than one large asteroid struck the Earth during the period when the dinosaurs were becoming extinct

Correct.   If several large asteroids struck over many years, their combined dust could potentially explain the extinction. Trent must rule out that possibility to conclude that asteroid impacts were not the cause.

Answer: (E)

Gilmore · Answer

Hello Team,
I am struggling to understand how to use the negation test for assumption Qs. Could someone please advise on how to approach which part of the statement to negate? Like, here in option (C) any event that takes place over a long period of time has many different kinds of causes. Should the negation be - any event that takes place over a long period of time has a single cause or Some events that take place over a long period of time do not have different kind of causes?

egmat · Answer

Hi Gilmore,

Great question, because this is the single most common slip with the negation test. Your second version is the correct one, and here's the rule that tells you why.

Negation means the  minimal  denial - "not necessarily true" - not the extreme opposite.

When you negate a statement, you are only saying "this isn't guaranteed." You are  not  flipping it to its strongest opposite. That's the trap in your first version.

Look at what option (C) actually claims:

" any  event that takes place over a long period of time has  many different kinds  of causes."

This is a universal claim:  all  long events → many kinds of causes. The logical negation of " all  X have Y" is always " at least one  X does  not  have Y." So the correct negation is:

- " Some  events over a long period do  not  have many different kinds of causes."

Your first version - "has a  single  cause" - overshoots. "Not many different kinds" could mean one cause, or two, or a few. Jumping straight to "a single cause" adds information the negation never requires. That's turning a  contradictory  into an  extreme contrary .

Now the payoff - why this proves (C) is wrong here.  The whole point of the negation test is: negate the choice, and if the argument collapses, it was a required assumption. Negate (C) correctly - "some long events don't have many kinds of causes" - and Trent's argument is completely unharmed. He never relied on (C) at all. Contrast (E): negate it to "more than one large asteroid struck," and Trent's reasoning falls apart instantly. That's the fingerprint of the real assumption.

Lock in the habit with a quick word-play drill:

- "All students passed." - negation?  At least one student did  not  pass.  (Not "all students failed.")
- "Every meal was expensive." - negation?  At least one meal was  not  expensive.  (Not "every meal was cheap.")

Same move every time: for "all/any," the negation is just "some are not" - never the mirror-image extreme.

Answer: E

Selena: Asteroid impact on the Earth caused the extinction of the dino

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Selena: Asteroid impact on the Earth caused the extinction of the dino

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards