LSAT Question Stem

Which one of the following is an assumption on which the argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is E. 

LSAT Question Complete Explanation

Let's first break down the argument in the passage and identify its structure. We have:

Premise 1: We could replace the old bridge with a concrete skyway.

Premise 2: Replacing the old bridge with a cable bridge would be more expensive than a concrete skyway.

Premise 3: The extra cost is justified by the importance of maintaining the beauty of the river crossing.

Conclusion: We should replace the old bridge with a cable bridge.

The question type for this problem is Necessary Assumption, which means we need to find an assumption that the argument depends on for the conclusion to be valid.

To help understand this better, let's use a simple example. Imagine you have a beautiful garden with an old, broken fence. You can replace the fence with a cheaper wooden one or a more expensive metal one. You decide to go with the metal fence because you want to maintain the garden's beauty. In this case, you're assuming that the metal fence is more beautiful than the wooden one.

Now, let's move on to the answer choices and evaluate each of them:

Answer Choice A: It is no more costly to maintain a cable bridge than a concrete skyway.

- The passage does not focus on maintenance costs, and the author seems to prioritize beauty over cost. So, this assumption is not necessary for the argument.

Answer Choice B: A concrete skyway would not have any practical advantages over a cable bridge.

- The passage does not discuss practical advantages, and the author's focus is on beauty. This assumption is not necessary for the argument.

Answer Choice C: The beauty of the river crossing must be preserved.

- This answer choice is tempting, but it's not necessary for the argument. The author could accept a lower standard of beauty and still advocate for the cable bridge due to its higher aesthetic appeal.

Answer Choice D: If the new cable bridge is built, most people who see it will think the extra money well spent.

- This answer choice focuses on people's opinions, which is not a strong basis for the argument. The author's focus is on the beauty of the river crossing, not popular opinion.

Answer Choice E: Building a cable bridge across Black River would produce a more aesthetically pleasing result than building a concrete skyway.

- This is the correct answer choice. The author's argument is based on the importance of maintaining the beauty of the river crossing, so it's necessary to assume that the cable bridge would be more beautiful than the concrete skyway.

In summary, the correct answer choice is E, as it is the necessary assumption for the argument to be valid. The author assumes that the cable bridge would be more aesthetically pleasing than the concrete skyway, which justifies the extra cost.