Final answer:
Some Southerners were interested in annexing Cuba for several reasons, but not because 'it was not controlled by any European power and would be easily acquired (option d) ,' as Cuba was a Spanish colony and Cubans were fighting for independence.
Step-by-step explanation:
The reason for annexation of Cuba that did not entice some Southerners was that Cuba 'was not controlled by any European power and would be easily acquired by welcoming Cuban population living on the Caribbean island' (d). This prospect is inaccurate because Cuba was under Spanish rule during the periods of annexation interest, and Spain had repeatedly refused offers from the United States to purchase the territory. Moreover, the Cuban population was struggling for their own independence from Spanish colonial rule, and they had deep-seated resistance to foreign domination.
Some Southerners were interested in annexing Cuba because it: (a) already had a large population of enslaved blacks, (b) could potentially be carved into several states, which would restore political balance in the Senate favoring slave states, (c) was located just off the United States' southern coast, and (e) was economically productive, particularly as a sugar-rich territory.