Suppose That a Recent Study Found an Increase in Heart

Multiple Choice

Suppose that a recent study found an increase in heart and lung disease among people aged 50‑60. Further study revealed that, compared to people 20 years younger, these individuals tended to smoke more during their young adulthood, because they were not aware of the health effects of smoking at that time. This difference between individuals raised at different times is an example of

A) the placebo effect
B) a cross‑sectional approach
C) a cohort effect
D) a prospective study