Which of the following is an example of correlated observations? Choose at least one.

A. Patients randomly assigned to treatment were compared with patients

randomly assigned to control.

B. Patients with a disease were compared with a group of disease-free controls.

C. A group of treated patients was compared with their pre-treatment values.

D. A group of exposed individuals was compared with a group of unexposed

individuals.

E. A group of cases were compared with sibling controls.