Concept:Transportation development in Tropical Africa faces major economic, physical, and planning challenges, but not all listed factors are considered primary problems.
Explanation:Inadequate capital limits the construction and maintenance of roads and railways.
Difficult terrain, such as dense forests and rugged landscapes, makes building transport networks costly and slow.
Poor planning leads to poorly connected routes and inefficient transport systems.
Climatic variation, however, is not a major problem specifically facing transportation development in Tropical Africa, though weather may affect travel conditions.
Answer:A. Climatic variation