According to this document why did the united states invade cuba

On April 11, 1898, President William McKinley asked Congress for authorization to end the fighting in Cubabetween the rebels and Spanish forces, and to establish a “stable government” that would “maintain order” and ensure the “peace and tranquility and the security” of Cuban and U.S. citizens on the island.

Explanation:

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yup! you are correct it is b.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).