In what context should the Oxford Comma be utilized?

The Oxford Comma should be utilized in the clarification of listing nouns in a sentence. An example being: "the monkeys, Claire, and Josh", the Oxford Comma being the second comma. An example without the Oxford Comma being: "the monkeys, Claire and Josh", creating confusion as to if Claire and Josh are monkeys, or if the monkeys are separate nouns.

What event caused the United States to declare war on Japan in the beginning of U.S. involvement of World War Two?

The December 7th 1941 Attack on the Hawaiian naval base, Pearl Harbor, pushed the United States to declare war on Japan.

What is the past-tense form of "Sam runs with his dog."?

The past-tense form is "Sam ran with his dog."