Concept:The sparse population of the West African middle belt is linked to difficult living conditions, not to the lack of modern industries.Explanation:Unfavourable climate makes the area less attractive for settlement.Inadequate infrastructure limits access to basic services and economic activities.Inadequacy of food reduces the carrying capacity of the land for human populations.However, the absence of heavy industries is a consequence of the low population and weak economy, not a root cause of the low population density.Answer:B. the absence of heavy industries in the area