Researchers studied the effects of exercise and other behaviors on the heart health of over 5000 residents of a city throughout their adulthood. This research procedure best illustrated a

A) regression toward the mean.
B) cross-sectional study.
C) scatterplot.
D) longitudinal study.

A longitudinal study involves studying the same group of individuals over an extended period of time. In this case, the researchers followed the residents throughout adulthood to study the effects of behaviors on their heart health, making it a longitudinal study. Regression toward the mean refers to a statistical phenomenon, a scatterplot is a graphical representation of data, and a cross-sectional study involves comparing different groups at a single point in time, none of which fit the description of this study.