Read the following description of an observational study and determine whether it is a cross-sectional, a case-control, or a cohort study. Explain your choice.
The Cancer Prevention Study II (CPS-II) examines the relationship among environmental and lifestyle factors of cancer cases by tracking approximately 1.2 million men and women. Study participants completed an initial study questionnaire in 1982 providing information on a range of lifestyle factors, such as diet, alcohol and tobacco use, occupation, medical history, and family cancer history. These data have been examined extensively in relation to cancer mortality. The vital status of study participants is updated biennially.