Concept:A natural harbour is a sheltered deep-water port formed by physical land features, not by artificial construction.Explanation:Among West African ports, Freetown in Sierra Leone is widely considered to have the best natural harbour.It is a large and deep harbour, well protected by the Sierra Leone Peninsula.Takoradi, Port Harcourt, and Monrovia are significant ports, but none is as naturally deep and sheltered as Freetown.Answer:C. Freetown