Concept:The main obstacle to livestock production in West Africa is biological, not economic or technological.
Explanation:Livestock farming in West Africa faces serious challenges from pests and diseases.
The tsetse fly transmits trypanosomiasis, which affects cattle and other animals.
Diseases such as rinderpest and foot-and-mouth disease cause high death rates.
Pests also reduce the quality of animals and lower productivity.
Other options like inadequate demand, traditional tools, or land tenure are less important than disease and pest pressure.
Answer:D. pests and diseases