Concept:Industries are often located near sources of raw materials to reduce production costs.
Explanation:The major industrial zones in Nigeria grew out of regions where cash crops were produced commercially.
Crops such as cocoa, groundnut, palm oil, and cotton attracted processing industries because they provided cheap and accessible raw materials.
For example, cocoa-producing areas in the southwest and groundnut-producing areas in the north became industrial centres.
Factories developed close to these farming areas to cut transport expenses and prevent spoilage of raw materials.
This pattern shows that the main origin of Nigeria's industrial zones is the presence of cash crops rather than migrant labour, self-help projects, or water resources.
Answer:D. The presence of cash crops.