Final answer:
The question is about a former Nixon aide who testified about the President's knowledge of the break-in.
Step-by-step explanation:
The subject of this question is History.
The question asks about a former Nixon aide who testified that the President did know of the break-in. The correct answer is John Dean.
John Dean was the White House Counsel to President Richard Nixon and testified during the Watergate scandal about Nixon's involvement. This event was a significant moment in American history, as it led to the resignation of President Nixon.
Learn more about Watergate scandal