"the prevalence of Alzheimer's dementia is very high among residents living in nursing homes. A student concludes that it is likely that living in a nursing home causes Alzheimer's dementia. What is the flaw in the student's reasoning? A. The student has failed to take into account other causes of Alzheimer's disease. B. The student is drawing a false conclusion; he is making the error of reverse causality. C. The student is using an inadequate sample size. D. The student is drawing a false conclusion by making the mistake of omitting critical variables such as the age and gender of the residents."