The correct answer is C) The British and French allied with the Ottomans.
The event in the Crimean War that occurred first was "The British and French allied with the Ottomans."
From October 1853 to February 1856, the Crimea War was fought in East Europe between Russia and the Allies, formed by Great Britain, France, the Ottoman Empire, and Sardinia.
It all started wneh the Christians in the Holy Land of Jerusalem, as the minority group they were, demanded the respect of their rights. Let's have in mind that in those years, the Ottoman Empire controlled the Holy Land. Then came other major factors such as France and England impeding Russia from conquest more territories because that represented a threat to western European countries. Nobody liked the idea of a stronger and more powerful Russia in the region.