While relevance is important for determining whether a source is useful for your specific needs, question number 3, "Is this research peer-reviewed?" is the best choice for evaluating the reliability of a source. Peer review is a process where other experts in the field evaluate research before it is published, which helps ensure the accuracy and credibility of the findings.
So, the best answer for evaluating the reliability of a source is 3. Is this research peer-reviewed?