Which type of study examines subjects at different ages to assess development?

The correct answer is a cross-sectional study. This type of study involves observing a population at a single point in time, which allows researchers to examine various subjects or groups at different ages simultaneously. By assessing individuals from different age groups, cross-sectional studies can provide insights into developmental differences related to age, as well as the prevalence of certain characteristics, health conditions, or behaviors across those age groups.

This approach allows researchers to capture a snapshot of the population, making it easier to identify trends and patterns that may be associated with developmental stages. It is particularly useful for generating hypotheses and understanding the relationships between age and various health outcomes without the time-consuming processes involved in longitudinal studies, where subjects are followed over time.

In contrast, the other types of studies have different focuses. A case-control study typically compares subjects with a specific condition to those without it, while a cohort study follows a group over time to assess outcomes related to exposures. Descriptive epidemiology focuses on providing an overview of health issues in a population without necessarily exploring relationships between age or developmental stages.