Select the Best Description of an Ecological/correlational Study Design

Select the best description of an ecological/correlational study design.

A) Examines relationships between a risk factor and a disease outcome at the population level
B) Creates a "snapshot" of an existing disease and factors that may be associated
C) Used to determine potential exposures in relation to a disease outcome; a group with the disease is recruited and compared to an equivalent group without disease
D) Examines relationships between an exposure and a disease outcome at the population level; subjects are followed over time and information on exposures is collected prior to the development of disease
E) Applies a controlled intervention to test the effect in prevention or treatment of disease; investigators assign who receives treatment and what treatment is given