This is a Necessary Assumption question. Could someone explain how Answer B is incorrect and Answer D is correct?
Answer B speaks to the gap (Detergent formulated for front-load dissolves more readily). Negating Answer B (Detergent formulated for front-load does NOT dissolve more readily) wrecks the conclusion because it removes the salient difference compared to ordinary detergent that the argument makes.
In contrast, Answer D provides a Sufficient Assumption to a Necessary Assumption question. Negating Answer D (It's not true that [detergent gets clothes really clean --> detergent dissolves readily in washer]) does not wreck the conclusion. Perhaps a detergent formulated for FLW simply requires less water to be just as effective as an ordinary detergent in a TLW. Or perhaps a detergent formulated for FLW has a special cleaning agent to compensate for not dissolving as readily. So on and so forth: In all cases, Sufficient does not equal Necessary.
Furthermore, working from wrong-to-right I eliminated Answer D as a trap. Answer D provides a "firmer" (conditional guarantee!) response more appropriate to a SA question. In contrast, Answer B provides a "softer" (comparative) response appropriate to most NA questions.
Thanks in advance for your help!
https://classic.7sage.com/lsat_explanations/lsat-70-section-1-question-21/
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