Passage Summary: Yu thinks a restaurant is lying about being pesticide-free because the owner shops at a store that buys from a farm that uses chemicals.

Conclusion: The claim that Jason’s Restaurant serves only pesticide-free food must be false.

Reasoning: The restaurant owner buys produce from a specific grocery store that receives shipments from a large farm known to use chemical pesticides.

Analysis: Yu’s argument is a bit of a leap; just because a store stocks produce from a 'bad' farm doesn't mean every item in the store comes from that farm. To weaken this, look for an answer that suggests the restaurant owner is a selective shopper—perhaps he only buys the organic, pesticide-free stock that the grocery store also carries. Yu is playing detective but might have missed the fact that grocery stores often have more than one supplier. A good weakener will decouple the store's general inventory from the restaurant's specific purchases.