Answer: A) a combination of results from many related studies.
Explanation:
Meta-analysis is defined as the study technique that is used to approach previous related research result in systematic manner to extract result about research content.It does not rely on conducting new research rather clinical test is conducted. This analysis is controlled and quantitative.
Other options are incorrect because correlation study, experimental research and interference approach option is not the field where metal analysis is used.Thus, the correct option is option(A).