Final answer:
Material does not need a citation if it's common knowledge, referring to information widely known and obvious, but specific data and quotes must always be cited.
Step-by-step explanation:
Material does not require a citation if it's common knowledge. Common knowledge refers to facts and information that are widely known and can be found in multiple sources, such that an educated adult would be expected to be familiar with this information without needing a citation. Examples include historical dates, well-known scientific laws, or who the current President of the United States is. However, specific data such as statistics, direct quotes, or ideas that are not widely recognized must always be cited to avoid plagiarism, and ethical attribution practices demand that we give credit through in-text citations and a Works Cited or References page, even if the work has already been cited once within a paper.