Concept:The First Republic in Nigeria was cut short by a military coup, and the main reason that made it possible was the high level of political corruption.Explanation:The politicians in the First Republic were widely seen as corrupt and self-serving.This corruption gave military officers a strong excuse to seize power and end the democratic government.Other issues like tribalism and the use of soldiers to stop riots existed, but they were not the major trigger.The coup plotters publicly pointed to corruption as the main reason for their action.Answer:A. nationwide corruption by the politicians