What Is True of Epidemiological Studies? Select All That Apply

What is true of epidemiological studies? Select all that apply.

A) The application of epidemiology requires knowledge of causal factors relative to the occurrence of specific health events in order to determine cause and effect.
B) Often epidemiological studies are observational and cross-sectional in design.
C) Epidemiological studies borrow from many disciplines, such as biostatistics, biology, and anthropology, and combines them into one viable science.
D) Knowledge of causal factors is often based on biostatistics to reveal measures of associations between causal factors and specific health events.