December 2010 LSAT Section 3 Question 19

In West Calverton, most pet stores sell exotic birds, and most of those that sell exotic birds also sell tropical fis...

hassay18 on October 22 at 09:24PM

Question about Choice B

Hello! I was wondering why choice B is wrong? While it does say that Tropical Fish and Exotic Birds, it also says "No pet stores that sell TF and EB sell gerbils" which is correct. Any store that sells both TF and EB do not sell gerbils. So then why is B wrong. Please kindly give a simple explanation. I get confused reading the big convoluted answers you guys sometimes give. Thanks.

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Emil-Kunkin on October 23 at 03:42PM

The rule tells us that if a pet store sells fish but not birds, then it must sell gerbils. That is if we have fish without birds, we know we have gerbils.

This tells us nothing about B. B is about stores that sell both birds and fish, a completely different set of stores than our rule was about.