The controversy at the heart of the ostend manifesto centered on the fate of:

ostend, belgium
nicaragua
cuba
louisiana

The correct answer is C. Cuba

Explanation:

The Osten Manifesto was a document written by diplomats of the U.S. in 1854 that aimed at persuading the Secretary of the U.S. to take actions in order to buy, seized or acquire the Cuban territory from Spain that had colonized it and to begin a war if Spain did not accept to leave the territory. This document was controversial mainly because it was influenced by the interests of slaveholders to expand slavery outside the U.S. territory to which Northern states opposed; also this document could determine the fate of Cuba as continuing under the Spanish rule or became a slave state under the U.S. government. Therefore, the controversy at the heart or essence of the Ostend Manifesto centered on the fate of Cuba especially in terms of the nation that would own the territory and whether this would be used as a slave state.