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.

i think it's the first one because doctors aren't the ones who get rid of the old needles. most of them time it's not even doctors who give you shots, it's nurses.