In a research paper, you generally do not need to cite:
- A) Familiar proverb
- B) Your personal opinion
- C) Anything you knew before doing the research
- D) Common knowledge
However, you should cite sources for specific information or data that is not considered common knowledge or your own thoughts.
Among the options provided, the correct answer would be anything that is not common knowledge, which is usually what needs to be cited. Therefore, if you are expected to select what doesn't need to be cited, the correct answer is:
D) Common knowledge — because you do not need to cite common knowledge in a research paper.