Evidence: We have had a particularly mild winter.
Assumption: A mild winter is not a weather condition which can cause sidewalk cracking.
Conclusion: It must be the case that the sidewalk cracking was caused by shoddy sidewalk materials and not weather conditions.
When we add our information, does it make the author’s argument more likely to be true? If the answer is yes, then we have our prediction for our answer. Remember, necessary assumption questions have almost an infinite amount of ways they could be worded, unlike a sufficient assumption question, which only has one answer. But more than likely our answer will bridge the gap between a mild winter and the weather conditions causing sidewalk cracking.
(A) The city supervisor has a reason to obscure the actual reason for the sidewalk cracking.
Does this make our conclusion that shoddy sidewalk materials, and not the mild winter, caused the sidewalk cracking more likely to be true? The answer is no. This is a tricky question because it wants you to make an assumption yourself: the city supervisor is lying because he or she does not want people to know the poor materials caused the cracking. But always remember, you should not make assumptions in the answers, and if you do, they should be minimal. Think about it a different way, is it necessary for our conclusion that the supervisor is lying? Is that a required assumption? No, it is not.
(B) Unseasonably cold weather is the only weather condition that leads to sidewalk cracking.
This answer should already look good based on our prediction earlier, but let’s plug it in to show why this answer is correct:
Evidence: We’ve had a particularly mild winter.
Assumption: Unreasonably cold weather is the only weather condition that leads to sidewalk cracking.
Conclusion: It must be the case that the sidewalk cracking was caused by shoddy sidewalk materials and not weather conditions.
Does this make the conclusion more likely to be true? The answer is yes. A clever reader may think: “but it hasn’t proven the conclusion has it? We know the winter could not have caused it, but isn’t it a jump from claiming the winter can not have caused it to the only possible cause being the materials?” If you thought this, you are absolutely correct. However, a necessary assumption question does not require us to prove the conclusion, only to find an assumption that makes the conclusion more likely to be true. We will tackle proving the conclusion 100% in sufficient assumption questions, but not here.
(C) Temperatures during the last winter were warmer than at any time in recent years.
How does this help prove our conclusion? What if last year, where temperatures were warmer in the winter, a record-breaking amount of sidewalk cracking occurred? This answer, without more, cannot help prove our conclusion. It needs to relate the weather and sidewalk cracking.
(D) The materials used for sidewalk construction differ from those used in the past.
So what if they differ? Do we know anything about the previous materials? What if the new materials caused much less cracking than the older materials? Wouldn’t that hurt our argument? This does nothing to bridge the gap between our evidence and conclusion.
(E) The unusually large amount of sidewalk cracking began during the last winter.
As with most wrong answers, this answer choice wants you to assume, but you should not make assumptions in an answer choice. Yes, an unreasonably large amount of sidewalk cracking may have occurred last winter, but do we know what the temperature was last winter? What if last winter was also a very mild winter? Wouldn’t that destroy our argument? This answer choice, on its own, does not bridge the gap.
