Alzheimer's disease results in a loss of cognitive ability beyond what is expected with typical aging. A local newspaper published an article with the following headline. Study Finds Strong Association Between Smoking and Alzheimer's The article reported that a study tracked the medical histories of 21.123 men and women for 23 years. The article stated that, for those who smoked at least two packs of cigarettes a day, the risk of developing Alzheimer's disease was 2.57 times the risk for those who did not smoke. (a) Identify the explanatory and response variables in the study. Explanatory variable: Response variable: (b) Is the study described in the article an observational study or an experiment? Explain. (c) Exercise status (regular weekly exercise versus no regular weekly exercise) was mentioned in the article as a possible confounding variable. Explain how exercise status could be a confounding variable in the study