Concept:Climax vegetation is the stable plant community reached when natural succession is undisturbed.Explanation:In the Savannah belt of Nigeria, the main human activity that repeatedly interrupts plant succession is the annual burning of vegetation.Bush burning destroys young plants and prevents the area from reaching its natural climax vegetation.Other activities like lumbering, mining, and animal grazing occur but are not as widespread or recurring in the Savannah as bush burning.Answer:D. Bush burning