Concept:A river basin is the area of land drained by a river and its tributaries.Explanation:The Cross River Basin and the Niger Basin are major river basins in Nigeria.The Sokoto Basin is also recognized as a river basin in the northwestern part of the country.The South Atlantic Basin, however, refers to the Atlantic Ocean basin, not a river drainage basin in Nigeria.Therefore, it is not a major river basin in Nigeria.Answer:The South Atlantic Basin (Option C) is not a major river basin in Nigeria.