The type of study design in this Prospective cohort study.
c) Prospective cohort study
Explanation:
It is the study that follows the overtime in a group of similar individuals who differs with respect to certain factors under the study to determine how the factors affect the rate of certain outcomes.
The testing may varies by the hypothesis given by the cretin patients that the age of 20 year of people affected by the lung cancer will be the highest among the heavy smokers, followed by the moderate and non smoking . it is test process of the individuals under the effective cause of the disease can be determined by method.