Concept:The Biu Plateau is a highland region in northeastern Nigeria with an average elevation above 100 metres.Explanation:The Biu Plateau is a prominent upland area formed by volcanic rocks.It stands well above the surrounding plains, with an average height exceeding 100 metres above sea level.The other listed regions, such as the North-Central Highlands and Adamawa Highlands, are not the correct answer here.Answer:A. Biu Plateau