A major advantage of cohort studies over case-control studies with respect to the role of a suspected factor in the etiology of a disease is that:
a. they take less time and are less costly.
b. they can utilize a more representative population.
c. it is easier to obtain controls that are not exposed to the suspected factor.
d. they permit direct estimation of risk of disease in those exposed to the suspected factor.
e. they can be done on a double-blind basis.

d. they permit direct estimation of risk of disease in those exposed to the suspected factor.

Explanation:

A major advantage of cohort studies over case-control studies with respect to the role of a suspected factor in the etiology of a disease is that they permit direct estimation of risk of disease in those exposed to the suspected factor.

i think you really need to revive you answer! : d

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.