Mark whether the following statements are true (T) or false (F)

a. Examples of eligibility criteria are time period, exposure to an agent of interest and having asthma.
b. International Classification of Disease version 10 (ICD-10) codes are only used for infectious diseases.
c. Diet over a 5 year period would generally be considered a time-varying exposure.
d. Prevalence is a measure of disease risk.
e. If A is correlated with B, then A necessarily caused the occurrence of B.
f. John Snow's research in cholera was considered a natural experiment