Answer:
It referred to the the people who were now taking the place to come with the meaning. "We the People of the United States"
Explanation:
This is called the frustration of purpose. It's a doctrine about how cases would be solved if unforeseen circumstances were to occur. A modern example would be if you took a mortgage but an earthquake completely destroyed your house. Due to the frustration of purpose, you could have your mortgage canceled because you don't have a house that the mortgage was for, so you wouldn't have to pay for it any more.
Lincoln was trying to appeal to Southern voters by picking Andrew Johnson as his running mate. These two men were actually very different politically speaking. Lincoln was a Republican, Andrew Johnson was a Democrat. Lincoln was from the Midwest US, Andrew Johnson was from Tennessee.
Lincoln knew that having a Democratic Vice President who once represented a Confederate state (Tennessee) would allow his presidency to appeal to a wider range of voters.
The answer is probably c or d
