Afive-year prospective cohort study has just been completed. the study was designed to assess the association between supplemental vitamin a exposure and mortality and morbidity for measles. the rr for incidence of measles was 0.75 and the rr for measles mortality was 0.5.

which statement is correct?

a. a cohort study is not an appropriate study design in this case because the
association between one exposure and two different outcomes is being
considered.

b. one of the problems that this study may have faced is individuals lost to
follow-up during the five-year period.

c. a cohort study is not a good design to study this association because measles is a very common disease.

regarding the rr reported above, which statement is correct?

a. exposure to vitamin a appears to protect against morbidity and mortality
for measles.

b. exposure to vitamin a appears to be a risk factor for morbidity and mortality for measles.

c. exposure to vitamin a is not associated with morbidity and mortality for measles.

d. exposure to vitamin a is a risk factor for morbidity and a protective factor for mortality for measles.