Critical Reasoning (CR) | Re: New CR Question from OG 2016 (Garlic Fields)

For better understanding, please note that an argument can also be made stronger by presenting a possible counter premise &
refuting it

Argument says : High Population of Mosquitoes -> Flood -> No Mosquito || Hence, Garlic is responsible for No Mosquito

Here, the author assumes that only some xyz from garlic is responsible for repelling mosquitoesand, there are no other factors such as the flood itself :

what if there were some other factors (eg: flood)?[counter premise]

[refuting counter premise] if flood was responsible
...

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