Final answer:
President Andrew Johnson was impeached for violating the Tenure of Office Act but was acquitted by the Senate and was not removed from office, which corresponds to option D.
Step-by-step explanation:
The correct statement about President Andrew Johnson's impeachment is D: Johnson was impeached for violating the Tenure of Office Act, but was not removed from office by the Senate.
President Andrew Johnson was impeached due to his actions that violated the Tenure of Office Act; specifically, he dismissed Secretary of War, Edwin Stanton, without the approval of the Senate. This dismissal was seen as a stepping stone to impeach Johnson, a move by the Radical Republicans to potentially replace him with the then president pro-tempore of the Senate, Benjamin Wade. Despite being impeached by the House of Representatives, a trial took place in the Senate where Johnson was narrowly acquitted, as it fell short of the required two-thirds majority by just one vote. Therefore, President Johnson remained in office until the end of his term.