GMAT Critical Reasoning (CR) | Re: In certain parts of rural Mongolia, many villagers suffer

My confusion with this one was with D. If people who do not use proper hygiene don’t do weekly checks, how do we know they would continue to not do so after reading the brochure? This was my confusion.

I actually chose A because a central tenant of the plan is a single, uniform solution outlined in the pamphlet to solve fungal infection for everyone in rural Mongolia. So if people react to the treatment differently, isn't it possible that the treatment will not help everyone? I think the problem