Concept:During Nigeria’s Second Republic, several parties existed at the national level. The main opposition to the ruling party came from strong political parties such as the Unity Party of Nigeria.Explanation:The Unity Party of Nigeria (UPN) was a major opposition party at the national level during the Second Republic.It was led by Chief Obafemi Awolowo and was highly influential in the western part of Nigeria.The UPN competed nationally and served as one of the principal opposition parties against the ruling party.Answer:B. UPN