Researchers Using a Longitudinal Study Design Observe

Researchers using a longitudinal study design observe:

A) a single participant over the course of his or her lifetime.
B) the same group of individuals on many occasions over a long period of time.
C) two groups of demographically similar participants with the same condition over a long period of time.
D) multiple groups of participants with the same condition at a single point in time, with each group being from a different age range.