Another researcher also decides to conduct a study to observe the association between smoking cessation among long-term smokers and obesity since it has been previously well documented in the literature that smokers tend to gain weight when they stop smoking. The researcher notes that among the individuals who gain weight, many of them have developed heart problems or other medical problems that typically prevent them from exercising as much as their counterparts. In this case the researcher notes that individuals who have developed the heart problems or other medical problems causing them to gain weight also came from family with a high prevalence of risk-taking behaviors so they consume unhealthy diets and are less likely to exercise in general than their counterparts. This is an example of which of the following?A ConfoundingB Effect modificationC. Recall biasD. Socially desirable response bias