The correct answer is (a) Both the Houses of the Parliament.
The President of India can be impeached only on the grounds of violation of the Constitution, treason, or other high crimes and misdemeanours. A motion for impeachment can be initiated only by either House of Parliament. If such a motion is passed by a majority of the total membership of that House and is agreed to by the other House by a similar majority, the President stands removed from office.
The Speaker of the Lok Sabha or the Chairman of the Rajya Sabha cannot initiate a motion of impeachment. However, they can preside over the proceedings of the House when the motion is being debated.
The process of impeachment is a very serious one and should be resorted to only in cases of grave misconduct by the President.