Aresearcher who wishes to see if existing theories are relevant to a current set of circumstances might be best suited to a approach.

The answer is “quantitative”.

Explanation:

Quantitative approach (which majorly involves the use of observations, measurements, and the analysis of data from questionnaires, surveys or polls, etc.) might be the best approach for a researcher wants to find out if existing theories are relevant to a current set of circumstances.

answer; they systematic design, collection, interpretation and reporting of information to marketers solve specific marketing problems or take advantage of market opportunities;