Question

The two Presidents who were impeached were:
1. Andrew Jackson and Richard Nixon
2. Bill Clinton and Richard Nixon
3. Andrew Jackson and Edwin Stanton
4. Bill Clinton and Andrew Johnson

Answer 1

The only two Presidents who were impeached were "4. Bill Clinton and Andrew Johnson," since the impeachment process is not taken lightly, and is very rare in the US. 

Answer 2

Answer:

4. Bill Clinton and Andrew Johnson

Andrew Johnson was impeached in 1868 for "high crimes and misdemeanors", which were detailed in 11 articles of impeachment.

Bill Clinton was impeached in 1998  for "high crimes and misdemeanors", which were subsequently detailed in 2 articles of impeachment.