You are investigating the role of physical activity in heart disease, and your data suggest a protective effect. Whilepresenting your findings, a colleague asks whether you have thought about confounders, such as factor. Under which ofthe following conditions could this factor have confounded your interpretation of the data?a. It is a risk factor for some other disease, but not heart disease.b. It is a risk factor associated with the physical activity measure and heart disease.c. It is part of the causal pathway by which physical activity affects heart disease.d. It has caused a lack of follow-up of test subjects.e. It may have blinded your study.