The correct answers are as followed:
2) The president can veto legislation passed by Congress.- This means that the president can stop a bill passed by Congress from becoming a law.
4) Congress has the power to impeach the president for misconduct.- Impeachment proceedings begin in the House of Representatives and continue in the Senate if enough evidence is found to have a trial.
6) The Supreme Court may declare laws unconstitutional- This power was given to the Supreme Court in the famous court case Marbury vs. Madison in 1803. This power is known as judicial review.