Match each type of epidemiology study with its description.

a. examination of past case histories and medical test results conducted on patients in an outbreak

b. examination of current case histories, interviews with patients and their contacts, interpretation of medical test results; frequently conducted while outbreak is still in progress

c. use of a set of test subjects (human or animal) and control subjects that are treated the same as the test subjects except for the specific treatment being studied

d. observing groups of individuals to look for associations with disease

e. a comparison of a cohort of individuals through the course of the study