The correct answer is D.
The impeachment process, as established by the US Constitution, gives Congress the power to impeach a president. It all starts in the House of Representatives, as a list of charges is developed by an individual. From there, a simple majority vote to remove the individual from office results in it going to the Senate. From there, 2/3rds of US Senators must vote to remove the person. If this happens, than the President is removed.
The closest any US President has ever come to being removed from office through this process is Andrew Johnson. He was one vote shy of being removed based on the Senate vote.
