The correct answer is (a) The President.
The President of India is the head of state and the supreme commander of the Indian Armed Forces. He/She is the one who summons the joint sitting of the Lok Sabha and Rajya Sabha under Article 108 of the Constitution of India.
The Speaker of the Lok Sabha is the presiding officer of the Lok Sabha, the lower house of the Parliament of India. He/She is elected by the members of the Lok Sabha.
The Chairman of the Rajya Sabha is the presiding officer of the Rajya Sabha, the upper house of the Parliament of India. He/She is elected by the members of the Rajya Sabha.
The Prime Minister of India is the head of government of India. He/She is the chief adviser to the President of India and is responsible for the day-to-day running of the government.
Article 108 of the Constitution of India states that:
“If at any time the President considers that it is necessary or expedient in the national interest so to do, he may summon a joint sitting of the Houses of Parliament for the purpose of deliberating on a Bill pending in either House.”
The President can summon a joint sitting of the Lok Sabha and Rajya Sabha only if a Bill has been passed by one House but not by the other. In such a case, the President can send the Bill to the other House for reconsideration. If the Bill is passed by the other House with or without amendments, it is sent back to the House in which it was originally passed. If the Bill is passed by both Houses with or without amendments, it is presented to the President for his/her assent.