How can the objectivity of research be enhanced?

Objectivity of research is enhanced through all three means, so All of the above holds.

Impartiality keeps the researcher's judgement free of prejudice.

Reliability, giving consistent results, reduces idiosyncratic error.

Validity, measuring the intended construct, keeps interpretation true to reality.

Each single means alone contributes only partly to objectivity.

Standardised, transparent procedures also let others verify the findings.