Which of the following best describes a longitudinal study?

A longitudinal study is characterized by the collection of data from the same subjects repeatedly over an extended period of time. This approach allows researchers to observe changes and developments in the subjects, making it ideal for studying trends, long-term effects of interventions, or natural progressions of conditions. By having multiple visits over time, researchers can gather rich, detailed data that captures the dynamics of the subjects' responses or behaviors.

This is distinctly different from studies that are short-term or focus on single-time assessments, both of which miss the depth of changes over time that longitudinal studies aim to capture.