He resigned because he'd already had enough trouble as president. Mainly the Watergate scandal. His plan was for him to step down and if he was arrested the vice president which would then be the vice president would pardon him. Also, if he didn't resign he'd likely be impeached anyway.
The 3/5ths compromise was like this
The south wanted their slaves to count as votes but the north disagreed, so every 3 slaves out of 5 count as 1 vote.
Answer:
B. Theodore Roosevelt became famous. Apex
Answer: Blitzkrieg
Germany's strategy was to defeat its opponents in a series of short campaigns. Germany quickly overran much of Europe and was victorious for more than two years by relying on a new military tactic called the "Blitzkrieg" (lightning war)
hope it helps.
I'm pretty sure A is the secondary source. All of the others come directly from the source/person, but an interview is getting someone else's view.