24. The original argument assumes that the only way that the asteroid impact could be the cause of the extinction of the triceratops is for either of the two results (climactic change or firestorm) to cause that extinction. However, other possibilities exist for attributing the extinction to the impact. Perhaps the asteroid landed directly on all the triceratops. Perhaps the asteroid had other effects, one of which caused the extinction.

The original argument:

	P1: W (asteroid) caused X (climactic change) and Y (firestorm).
	P2: We cannot show that X caused Z (triceratops extinction).
	P3: We cannot show that Y caused Z.
	A: Only if X or Y caused Z can we claim that W caused Z.
	_________________________________________
	C: We cannot claim that W caused Z

 

 

 

 

 

 

 

(D) parallels:

	P1: W (flooding) caused X (furnace damage) and Y (electrical short).
	P2: Fire investigators could not show that X caused Z (fire).
	P3: Investigators could not show that Y caused Z.
	A: Only if X or Y caused Z can we claim that W caused Z.
	_________________________________________
	C: We cannot claim that W caused Z

 

 

 

 

 

 

 

(A) states "doubt", whereas the original argument is concerned with showing. Also, (A) refers to the two things (Leon and Pam) together for an effect in the conclusion, whereas the original considers the two things (climactic change and firestorm) separately for an effect.

 

(B) works this way:

	P1: Quite sure that C and L are only candidates.
	Secondary Conclusion: Can be quite sure that either C or L will win.
	_________________________________________
	C: Either we know that C will win or we know that L will win.

 

 

 

 

 

(C) works this way: It has not been proven that X or Y caused Z, therefore it has been proven that neither X nor Y caused Z.

 

(E) works this way:

	P1: Good reason to believe that Y (tides) caused Z (flooding).
	P2: Good reason to believe that W (sun) or X (moon) caused Y.
	_________________________________________
	C: Reasonable to maintain that W or X caused Z.

 

 

 

 

 

25. This question tests your ability to extract the conclusion, which is the second half of the first sentence -- from the comma to the period. Change "similar effect" to "benefit the wealthy" and find a paraphrase, found in (E). If you read the question stem first and thus know that you are seeking the argument's main point, then once you have found the main point at the beginning of the passage, you can skim quickly over the other sentences in the passage, see that they are premises (and thus you do not need to read the details), and move on to the choices.

(A) refers to the first half of the first sentence.

(B) contains part of a premise.

(C) is a secondary conclusion contained in the second sentence.

(D) is a secondary conclusion that appears at the end of the passage.