Which nations comprised the Triple Entente before the United States joined in 1917?

The correct answer is based on historical alliances formed in the lead-up to and during World War I. The Triple Entente was a formal understanding among three major powers: Great Britain, France, and Russia. This alliance was established to counterbalance the threat posed by the Triple Alliance of Germany, Austria-Hungary, and Italy. The inclusion of Serbia can be seen as significant due to its connection to Russia, especially following the assassination of Archduke Franz Ferdinand, which sparked the war.

In this context, Great Britain, France, and Russia formed an organized alliance with mutual support in military matters, which became essential once the war began. The later involvement of the United States in 1917 added a significant new ally but did not shape the original members of the Triple Entente.

Other options suggest different groupings of nations, either combining nations involved in the Triple Alliance or including other countries that were not part of the Entente's formal arrangement. Such mischaracterizations of the alliances before the U.S. entry into the war clarify the importance of recognizing the specific members of the Triple Entente during this period in history.