Which sentence uses the Oxford comma correctly?

• A. The Indian Removal Act, the Compromise of 1850, and the Mexican-American War represent three dark moments in America's history.
• B. The Indian Removal Act, the Compromise of 1850 and the Mexican-American War represent three dark moments in America's history.
• C. The Indian Removal Act the Compromise of 1850, and the Mexican-American War represent three dark moments in America's history.
• D. The Indian Removal Act the Compromise of 1850 and the Mexican-American War represent three dark moments in America's history.

Answer: (A)

The serial (Oxford) comma is the comma placed before the conjunction in a list of three or more items. Here, the three items are the Indian Removal Act, the Compromise of 1850, and the Mexican-American War. Including a comma after the second item before the conjunction “and” makes the list clearly three items, which is exactly how it should read: the Indian Removal Act, the Compromise of 1850, and the Mexican-American War. The other versions drop that comma, which can read as two items or create ambiguity about the last two items. Remember, the hyphenated Mexican-American War counts as one item, so the list has three items in total.