Concept:Farm power is the energy used for agricultural work, classified by its source of origin.
Explanation:The principal sources of farm power in West Africa are human, animal, and mechanical.
Human power involves manual labour performed by farm workers.
Animal power uses draught animals such as oxen, donkeys, and horses.
Mechanical power comes from machines like tractors and tillers.
These three sources are widely available and practically used by farmers in the region.
Wind, solar, and electrical power are not regarded as the main farm power sources in West Africa.
They are either supplementary, unreliable, or less developed for routine farm operations.
Therefore, the correct grouping of the main sources is human, animal, and mechanical.
Answer:B. human, animal and mechanical