In a cohort study examining the association of lung cancer w

In a cohort study examining the association of lung cancer with the use of e-cigarettes, it is essential that:

The population to be followed is representative of the general population

All cases identified as having lung cancer at baseline should be removed from the cohort

The study is done in a double blind fashion

There are equal numbers of persons in the exposed and not exposed groups

Follow-up is greater than 75% in both the exposed and not exposed groups

	A.	The population to be followed is representative of the general population
	B.	All cases identified as having lung cancer at baseline should be removed from the cohort
	C.	The study is done in a double blind fashion
	D.	There are equal numbers of persons in the exposed and not exposed groups
	E.	Follow-up is greater than 75% in both the exposed and not exposed groups

All cases identified as having lung cancer at baseline should be removed from the cohort