Concept:Nigeria's major peacekeeping missions in 1993 were in Liberia and Somalia.Explanation:In 1993, Nigerian troops served in Liberia under the Economic Community of West African States Monitoring Group (ECOMOG).They also served in Somalia under the United Nations Operation in Somalia II (UNOSOM II).These were the two main peacekeeping assignments for Nigerian troops in that year.Answer:D. Liberia and Somalia