Answer:
B) One of his secret tapes revealed that he had ordered a cover-up.
Step-by-step explanation:
The tapes had more than 3500 hours of recorded material, and around 200 is referring to the Watergate scandal. This scandal was an event in 1972. when burglars were caught stealing documents and wiretapping phones in the Democratic National Committee office in the Watergate complex. This was connected to Nixon and his reelection campaign and he tried hard to cover up the scandal.
However, when the tapes have been searched, they found initial plans of the cover-up where Nixon is forming a plan to make claims that national security was involved and his plans to prevent the investigation.
Due to this disgrace, Nixon resigned on 8th of August 1974