The correct answer is A. 1917.
The United States declared war on Germany on April 6, 1917. The following month, on May 31, 1917, British forces captured Baghdad from the Ottoman Empire. On December 9, 1917, British forces captured Jerusalem from the Ottoman Empire.
Option B is incorrect because Britain defeated Turkey and captured Baghdad and Jerusalem in 1917, not 1918.
Option C is incorrect because the United States did not declare war on Germany until 1917, not 1919.
Option D is incorrect because the United States did not declare war on Germany until 1917, and Britain did not defeat Turkey and capture Baghdad and Jerusalem until 1917.