The context refers to an example in support.
"Cited" in option A is correct as it is used to refer to (a passage, book, or author) as evidence or example/justification of an argument or statement.
"Sited" in option B indicates a building location in a fixed place.
"Citted" in option C and "sitted" in option D are incorrect as these words do not exist.
Thus, option A is correct.