Answer:
Based on the given options, the cause of World War I that was not mentioned is: "The sinking of the Lusitania in the Atlantic Ocean."
While the assassination of Archduke Franz Ferdinand by Gavrilo Princip, the competition between Germany and Great Britain to dominate the oceans, and the European nations' scramble for colonies were all contributing factors to the outbreak of World War I, the sinking of the Lusitania is not listed as a cause.
The sinking of the Lusitania, a British passenger ship, by a German submarine occurred during the war and had a significant impact on public opinion, particularly in the United States. However, it was not one of the direct causes that led to the start of the war. The sinking of the Lusitania took place in 1915, while the war began in 1914.