Concept:Agricultural productivity is reduced mainly by factors that destroy crops, reduce yields, or remove farm labour from rural areas.
Explanation:Pests and diseases damage crops directly, so they lower farm output.
Unfavourable weather conditions like drought and floods reduce yields significantly.
Illiteracy prevents farmers from adopting improved farming methods, which limits productivity.
Urban-rural migration is the movement of people from towns back to villages.
Such movement tends to increase the supply of farm labour rather than reduce it.
Therefore, it has the least adverse effect on agricultural productivity in West Africa.
Answer:C. Urban-rural migration