Why is D the correct answer?

Hello @cjahangiri, Peter never argues that moderate alcohol consumption is the best way to create an inhospitable environment for bacteria. He doesn't say that moderate alcohol consumption is the most beneficial. This is why C doesn't matter. There could be a more beneficial substance, but it wouldn't affect Peter's argument. He simply argues that it is beneficial. It seems that you understand the real flaw, which is that Peter makes a claim about alcohol in general. This is not supported by the premise about moderate consumption of alcohol.

Thank you! So going forward I should stick to only what is mentioned in the passage.

Absolutely, you should focus on what the argument says specifically. Thank you for your question.