Why did the United States enter World War I?

What does this answer mean?

The United States entered World War I because Germany attacked U.S. ships and to support the Allied Powers against the Central Powers. USCIS accepts three answers: because Germany attacked U.S. (civilian) ships; to support the Allied Powers (England, France, Italy, and Russia); or to oppose the Central Powers (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria).

The war began in Europe in 1914, and the United States stayed out at first. In early 1917, Germany resumed unrestricted submarine warfare, meaning its submarines would attack ships at sea without warning, including American ships. Around the same time, Americans learned of the Zimmermann Telegram, a secret German message offering Mexico help to recover U.S. territory if it joined the war against the United States.

President Woodrow Wilson asked Congress to declare war, and on April 6, 1917, the United States entered the war against Germany. The fighting ended with an armistice on November 11, 1918.

At the interview, say "because Germany attacked U.S. ships."