The answer is (C) The Balkan War.
Explanation for each option:
A. The Crimean War: This war took place from 1853 to 1856 and primarily involved the Ottoman Empire, Russia, Britain, France, and Sardinia. The main conflict was over the rights of Christian minorities in the Holy Land, which was part of the Ottoman Empire. While the war did weaken the Ottoman Empire, it did not result in the loss of Greece, Serbia, or Bulgaria.
B. The Bolshevik War: This term is not commonly used in historical contexts. It might refer to the Russian Civil War (1917-1923) following the Bolshevik Revolution, but this conflict was primarily within Russia and did not directly involve the Ottoman Empire losing control of Greece, Serbia, or Bulgaria.
C. The Balkan War: The Balkan Wars (1912-1913) were two conflicts that led to significant territorial losses for the Ottoman Empire in the Balkans. The First Balkan War (1912-1913) saw the Ottoman Empire lose almost all of its European territories, including Greece, Serbia, and Bulgaria. This is the correct answer.
D. The Easter War: There is no significant historical event known as the Easter War that involved the Ottoman Empire losing control of Greece, Serbia, or Bulgaria. This option is incorrect.
Therefore, the correct answer is (C) The Balkan War.