The Joint Sitting of the Lok Sabha and Rajya Sabha under Article 108 is summond by

The answer is A) The President. Under Article 108, when a Bill passed by one House is not passed by the other, or the Houses disagree on its final form, or the other House has not acted for six months, the President may summon both Houses to meet in a joint sitting. The summoning power lies with the President alone, on the advice of the Union Council of Ministers, so it is not a power of the presiding officers.

• B) Speaker of Lok Sabha: Wrong for summoning. The Speaker presides over the joint sitting under Article 118(4), but presiding is different from summoning.
• C) Prime Minister: Wrong. The PM advises the President, but the formal summons is issued in the President's name.
• D) Chairman of Rajya Sabha: Wrong. The Vice-President is ex officio Chairman and has no role in convening a joint sitting.

The core concept is the mechanism for resolving legislative deadlock between the two Houses, which is an ordinary (non-Money) Bill matter. Money Bills are outside Article 108 because the Lok Sabha's will prevails under Article 109. For Mains, this links to debates on bicameralism and the Rajya Sabha's role. Joint sittings have been used only three times (1961, 1978, 2002).

Trap: Aspirants confuse the presiding officer with the summoning authority, and pick the Speaker because the Speaker presides.