A type of observational study that follows a group of participants over a period of time, examining how certain factors affect their health outcomes is referred to as:

Correct option is B

Explanation:
A cohort study is a type of longitudinal observational study where researchers follow a group of people (a cohort) over time to observe how exposure to various factors (e.g. lifestyle, environment, or medication) affects the development of certain health outcomes. It can be prospective (looking forward) or retrospective (looking back at historical data).
Information Booster:
Cohort studies are useful in determining risk factors and causality, especially in epidemiology. They are different from case-control studies, which start with an outcome and look backward to find exposures. Experimental studies, unlike cohort studies, involve intervention by the researcher. Case-crossover studies are used to study the effects of transient exposures on the risk of acute events.