The answer is B. Spain.
Christopher Columbus discovered the America’s in an area very close to modern day Cuba. The Caribbean throughout the age of colonization remained more or less in majority control of the Spanish. Around the time when Spain’s empire was decline in the fallout of the Napoleonic Wars, America wanted to expand their borders and become a world power. Since Spain controlled Cuba and America wanted to expand in that area, Spanish brutality to the local population and hostility was justification for the war.