Concept:Agricultural development is mainly hindered by institutional, infrastructural, and biological factors, not by a normal climatic element such as rainfall.
Explanation:Poor transportation restricts the movement of farm inputs, equipment, and harvested produce in West Africa.
Land tenure systems limit farmer access to land and reduce the incentive to make long-term improvements.
Pests and diseases cause serious losses to crops and livestock, thereby reducing agricultural output.
These are all recognized constraints on agricultural development in the region.
Rainfall, on the other hand, is a climatic necessity for crop growth rather than a structural barrier to agricultural development.
Hence, rainfall does not belong to the same category as the other listed factors.
Answer:B. rainfall