In a cohort study, the advantage of starting by selecting a defined population for study before any of its members become exposed, rather than starting by selecting exposed and nonexposed individuals, is that:
a. The study can be completed more rapidly
b. A number of outcomes can be studied simultaneously
c. A number of exposures can be studied simultaneously
d. The study will cost less to carry out
e. a and d
Answer: c. A number of exposures can be studied simultaneously