I think it is answer A, Common law because it is derived from custom and judicial precedent.
Talking to a person you do not know, an email to a business representative, and similar would be situations where someone would have to use formal language.
<span>Aftermath. One year later, however, in Worcester v. Georgia, 31 U.S. 515 (1832), theU.S. Supreme Court ruled that the Cherokee Nation was sovereign. According to the decision rendered by Justice John Marshall, this meant that Georgia had no rights to enforce state laws in its territory.</span><span>
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The answer is:
3. <span>they include a bibliography and citations to credit the sources
Good Luck! :D
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To keep people from breaking rules and to keep our world in a good place