Answer: C. The United States participated in negotiations to establish national elections that would reunify North and South Vietnam.
Step-by-step explanation:
The Geneva Accords as they were known, were created after negotiations in Geneva where the representatives of 8 countries including the United States, met to forge a path towards the reunification of North and South Vietnam.
It was agreed during the negotiations that, an election to unify the two nations would be held in 1956, 2 years after the negotiations which occurred between May to July 21, 1954.
As President Lyndon Johnson only became president in 1963, this was not done under his administration.