Concept:The Fourth Republic in Nigeria began in 1999, and the body legally empowered to conduct that election was the Independent National Electoral Commission (INEC).
Explanation:INEC was established by the 1999 Constitution to organise, conduct, and supervise elections in Nigeria.
It conducted the 1999 presidential and national assembly elections that marked the start of the Fourth Republic.
The earlier bodies, FEDECO, NEC, and NECON, served during previous republics and transitional periods, not the 1999 election.
Therefore, the commission that ushered in the Fourth Republic is INEC.
Answer:A. INEC