LSAT 146 | Section 2 | Logical Reasoning: Q21

LR Question 21 Explanation

QUESTION TEXT: A local marsh would need to be drained before the…

QUESTION TYPE: Principle – Parallel

CONCLUSION: The city shouldn’t let the office complex be built until there is a scientific assessment of how the marsh maintains the city’s well water.

REASONING: Building the office complex would require draining a marsh. But marches often help purify groundwater.

ANALYSIS: The argument’s structure is as follows:

1. Doing the thing would require destroying something that might be helpful
2. So, we should check if the thing is helpful before allowing the thing to happen

If you think of arguments in abstract terms like this, it helps to skim the answers to see what’s correct. The conclusion should be the first place to look. It needs to say something like “we shouldn’t do it yet” or “we should only do it once we’ve done the other thing”.

You can eliminate three answers this way! Only two have the right conclusion type. That’s how you flip parallel questions from being slow to fast.

___________

1. The conclusion in this answer doesn’t match. In the stimulus, it said “we shouldn’t build until we do the report”. This implies we might end up building, if the report is favourable. In this case, the argument just flat out rejected building.
    
   This has the same subject matter: the environment and construction. But the structure is wrong. You don’t need the same subject matter to parallel an argument; an answer which uses the same subject matter tends to be a trap.
2. CORRECT. This matches. In the stimulus, we had to test the marsh to make sure that losing it wouldn’t cause a problem. Here, we have to test the product to make sure defects won’t cause a problem. In each case, there is a possible problem associated with going forwards, and we have to rule out the problem before proceeding. The conclusion matches: Yova should not yet launch its product….but maybe it should after the test; if the results are good.
3. This conclusion is in the right format: it says we shouldn’t release the report until we’ve done the safety check.
    
   However, the reasoning doesn’t match. In the stimulus, the issue was that losing the marsh might cause problems. Here, the only problem is a matter of timing: we simply need more time before finishing the safety check. But there’s no question that once that is done, we’ll release the report. Whereas with the marsh, it’s possible the building shouldn’t be built at all. (If the marsh does turn out to purify water.)
4. The conclusion is wrong. It recommends one of the two ways in which the highway should be built. But in the original, the only way to build the building would be to drain the marsh. And if the marsh purified water, it wouldn’t make sense to drain it.
    
   Whereas in this case, the reasoning simply indicates which route causes less damage.
5. This conclusion is completely wrong. It says we should build, no matter what. Whereas in the original argument, we might not build, if the marsh has benefits.
    
   For this to match, the stimulus should have said “We’ll need to drain the marsh and lose its water purification to build the building. But if we don’t build it, we’ll have many homeless people. So we absolutely must build the building.”