Which of the following describes a retrospective study?

A retrospective study is characterized by its focus on examining past events or exposures to determine their relationship with current outcomes. In this type of study, researchers look back at historical data, often using medical records, interviews, or existing databases, to gather information about subjects' previous exposures or risk factors and how these may relate to health outcomes that have already occurred.

This approach is beneficial because it allows researchers to study variables that may have influenced outcomes without needing to conduct lengthy follow-up periods that prospective studies require. By analyzing existing data, researchers can uncover associations and generate hypotheses about causal relationships in a time-efficient manner. Thus, the choice that describes a retrospective study accurately emphasizes its nature of examining historical events to understand their effects on present conditions.