what is common knowledge and how do you know whether something is 100% common knowledge or not to avoid plagiarism?

also is there any website or tool that can tell you whether or not something is common knowledge or not? if not then how do plagiarism checkers detect common knowledge?

Submitted March 06, 2021 at 11:17AM by Acomplished864 https://ift.tt/3sNmQNc