For there to be a thriving population of turtles in a pond, conditions

Question

For there to be a thriving population of turtles in a pond, conditions at that pond must be beneficial to turtles. The water in Wallakim Pond, unlike that in Sosachi Pond, is acidic. Thus, there must not be a thriving population of turtles at Wallakim Pond.

Which one of the following, if assumed, enables the argument's conclusion to be properly drawn?

(A) If the water in a pond is not acidic, the conditions at that pond are beneficial to turtles.

(B) The most important factor that determines whether a pond will have a thriving turtle population is the acidity of the water.

(C) The water conditions at Sosachi Pond are more beneficial to turtles than are the water conditions at Wallakim Pond.

(D) Wallakim Pond would have a thriving population of turtles if it were not acidic.

(E) The conditions at a pond are beneficial to turtles only if the water in the pond is not acidic.

PaceOven · Answer

How can it be E please explain
IMO it's C

guddo · Answer

For there to be a thriving population of turtles in a pond, conditions at that pond must be beneficial to turtles. The water in Wallakim Pond, unlike that in Sosachi Pond, is acidic. Thus, there must not be a thriving population of turtles at Wallakim Pond. 
 
Which one of the following, if assumed, enables the argument's conclusion to be properly drawn?

The argument says a thriving turtle population requires beneficial conditions. Wallakim Pond has acidic water.  The missing link  is that acidic water means the pond’s conditions are not  beneficial to turtles .

(A) If the water in a pond is not acidic, the conditions at that pond are beneficial to turtles.

This is the wrong direction. It says nonacidic water is enough for beneficial conditions. But we need to know that acidic water rules out beneficial conditions.

(B) The most important factor that determines whether a pond will have a thriving turtle population is the acidity of the water.

This is not enough. Even if acidity is the most important factor, acidic water might still allow a thriving turtle population.

(C) The water conditions at Sosachi Pond are more beneficial to turtles than are the water conditions at Wallakim Pond.

This is not enough. Wallakim could be less beneficial than Sosachi but still beneficial enough for turtles to thrive.

(D) Wallakim Pond would have a thriving population of turtles if it were not acidic.

This does not prove that Wallakim lacks a thriving turtle population now. It tells us what would happen if the pond were not acidic, but not what follows from its being acidic.

(E) The conditions at a pond are beneficial to turtles only if the water in the pond is not acidic.

This is correct. This means acidic water rules out beneficial conditions. Since Wallakim’s water is acidic, its conditions are not beneficial to turtles. Since thriving turtles require beneficial conditions, Wallakim cannot have a thriving turtle population.

Answer: (E)

Shashwat_hai · Answer

D-> A if B -> (B -> A)

E-> A only if B -> (A -> B)

Took a lot of time to understand how "only" changes the seemingly sufficient condition to necessary condition.

FreshScale · Answer

can you explain how is E: A only if B deduces to A -> B??

yc168 · Answer

Understanding and memorizing the following indicator words may be helpful in recognizing the conditional relationship:
   To introduce a 
 Sufficient Condition : 
 To introduce a 
 Necessary Condition : 
 
  If
When
Whenever
Every
All
Any
Each
In order to
People who
 
 Then
Only
Only if
Must
Required
Unless
Except
Until
Without
Precondition

egmat · Answer

Hi FreshScale,

You're reacting to Shashwat_hai's line that " A only if B " becomes  A → B , and that's exactly the piece worth slowing down on. The trick is that the words "if" and "only if" point in  opposite directions .

The rule: 
- "A  if  B" → B is enough to guarantee A →  B → A 
- "A  only if  B" → B is  required  for A; without B you cannot have A →  A → B

The phrase after "only if" is always the  necessary  condition. Whatever comes after "only if" is the thing you can't do without.

Feel it with an everyday sentence:

"You can graduate  only if  you pass the final."

Does graduating force you to have passed? Yes - no pass, no graduation. So  graduate → passed . Notice it does  not  run the other way: passing the final doesn't guarantee you graduate (you might fail another requirement). That's precisely  A → B , not  B → A .

Now map it back to E.  Let A = "conditions are beneficial" and B = "water is not acidic." E says:

"conditions are beneficial to turtles  only if  the water is not acidic"

Thereforebeneficial → not acidic  (A → B). Take its contrapositive:  acidic → not beneficial . Wallakim's water  is  acidic, so its conditions are  not beneficial  - and since a thriving population needs beneficial conditions, Wallakim can't have one. That's the bridge the argument was missing.

Quick self-test - turn the one knob: 
- "Beneficial conditions  if  the water is not acidic" → which direction? (not acidic → beneficial - that's actually choice A, the wrong one!)
- "Beneficial conditions  only if  the water is not acidic" → beneficial → not acidic (choice E).

See how flipping "if" ↔ "only if" flips the arrow - and how that's exactly the difference between the trap answer A and the correct answer E.

Answer: E

egmat · Answer

Hi PaceOven,

I see why C is tempting: the argument leans on the contrast between Sosachi and Wallakim, and C looks like it's spelling out that contrast. Let me show the exact gap it leaves.

First, trace what the conclusion actually needs. The argument tells us:

- A thriving turtle population  requires  beneficial conditions.
- Wallakim's water is  acidic .

To conclude "no thriving population," you must be able to say Wallakim's conditions are  not beneficial . The only fact you have about Wallakim is that it's acidic - so you need a bridge that turns  acidic  into  not beneficial .

That's exactly what E does.  E says conditions are beneficial  only if  the water is not acidic. Flip it: acidic => not beneficial. Wallakim is acidic => its conditions aren't beneficial => no thriving population. The chain closes.

Why C falls short:  C only says Sosachi's conditions are  more beneficial than  Wallakim's. "More beneficial than" is a comparison - it never establishes that Wallakim's conditions fail the bar. Wallakim could be  less  beneficial than Sosachi and  still be beneficial enough  for turtles. So the conclusion doesn't follow. C is true-sounding but does nothing to the argument's actual link.

Here's the one-knob test to feel it:

- "Team A scored  more  than Team B." -> Can you conclude  Team B lost ? No - both could have won their games.
- "You can pass  only if  you score above  60 ." -> Now if someone scored below  60 , you  can  conclude they failed.

See the difference? A comparison (C) never forces one side below the line; an "only if" rule (E) does. That's why E is the assumption that makes the conclusion airtight.

Answer: E

For there to be a thriving population of turtles in a pond, conditions

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To introduce a Sufficient Condition:	To introduce a Necessary Condition:
If When Whenever Every All Any Each In order to People who	Then Only Only if Must Required Unless Except Until Without Precondition

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For there to be a thriving population of turtles in a pond, conditions

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