The correct answer is:
D. an outside mine.
Explanation:
The U.S.S. Maine was a battleship that had been sent to protect American lives and properties in Cuba during the revolt against the Spaniards. It exploded and sank in Havana harbor in January 1898, and was the determinant factor for the United States to intervene against the Spaniards after investigations concluded that the explosion was caused by an external cause (a mine), and that Spanish people plotted against the Americans.
