The entire population of a given community is examined, and all who are judged to be free from bowel cancer are questioned extensively about their diets. These people then are followed for several years to see whether or not their eating habits will predict their risk of developing bowel cancer.

a. Cross-sectional study
b. Case-control study
c. Prospective cohort study
d. Historical prospective cohort study
e. Clinical trial
f. Community trial

type of study design is Prospective cohort study

Explanation:

This study follows overtime in a group of similar people who differ from some of the factors in the study to determine how factors may affect the outcome rate. Tests may vary depending on the hypothesis given by Cretin patients who are cigarette patients, who are most likely to be smokers, then most likely to be over 20 years of age, with a high rate of lung cancer. The effective cause of the disease is determined by the method of screening of the individuals below.