The Same Epidemiologic Question Regarding the Effectiveness of a Treatment

The same epidemiologic question regarding the effectiveness of a treatment can be addressed by several studies.Often,there are inconsistencies between such studies.What can be done when such discrepancies are found?

A) Trust the study done by senior researchers.
B) Trust the study with bigger sample size.
C) Conduct a systematic review with a meta-analysis.
D) Trust the study that makes more sense.
E) None of the previous.