It should summarize the whole truth.
Some topics have thousands of research papers, published world-wide: for example questions related to cancer; tobacco use; the safety of foodstuffs; etc.
With thousands of papers published, it would be easy (but wrong) to select only a few which show whatever you want, and especially where the conclusion contradicts normal findings from a majority of other studies.
For complex topics, where studies disagree, a good answer should show a review of the literature and not just cite a single study (appropriate references might be 'survey' studies, which summarise the conclusions of other studies).
It's not that the majority opinion is always necessarily correct, but an answer should properly cover the topic (which should include at least an acknowledgement of majority opinions).