Answer: C. Common law
Explanation:
Since the judge cites precedent when delivering a ruling in a case, then he is harkening back to a practice that was begun in a set of common laws.
Common law refers to a body of unwritten laws that was based on legal precedents that was established by the courts. It should be noted that common law influences the process of decision-making in cases whereby it's difficult to determine the outcome of the case based on the written rules of law.
