Business people must understand the various origins of laws/rules/regulations that affect the day-to-day and strategic decisions of their businesses. All of the following are considered sources of law in the United States except one. Mark the one that is not a source of law.

a. A mayor's opinion that a business should not locate in the city. b. Governor's order to restrict business activity. c. Administrative agency rule fining a business for pollution. d. Congressional vote to regulate trade with a foreign country. e. Judge opinion stating that businesses must serve all people.