Answer:
b. Prospective cohort study
Explanation:
Prospective cohort study -
It is a type of cohort study, which require certain period of time to get the result on a group of similar or equivalent peoples, that shows variation on certain factor, which is studied, is referred to as the prospective cohort study .
The time period for such studies usually varies from several months to years, in order to get the result in a very precise and brief manner .
The studies can be done on various topics like smoking habits , alcohol consumption, sleep cycle, diseases etc.
Hence, from the given scenario of the question,
The survey asking for dietary intake , is an example of the prospective cohort study.