The answer is A.
The subject of the sentence (the person or thing doing the action) has to agree in number with the verb (the word representing the action).
The type of method of incorporating data that i would use in emphasizing a particularly authoritative source would be summarizing and also quoting. This would avoid plagiarism and other offenses and also summarizing some data in order to prove the evidence
A paper that show legal ownership of property a deed.
Hope this helps. :)
