Which study approach gives the researcher control over items like selection of a source population, and the content and wording of a questionnaire?

Primary studies.

Explanation:

The study approach which gives the researcher control over items like selection of a source population, and the content and wording of a questionnaire is known as primary studies.

A primary study is a research methodology that is typically focused on having the researcher collect data directly rather than being dependent on a research that was conducted earlier or previously.

This ultimately implies that, a primary study avails a researcher the opportunity to own and have dominion or control over the entire research process.

a.) carbohydrates

i believe

because health skills are tools and strategies and also practical skills are also something you need to learn (like tools and strategies) and put it in reality.