Explanation:

The principle of collective responsibility is a cornerstone of India's parliamentary democracy. - **Option A (Lok Sabha):** This is the correct answer. According to Article $75(3)$ of the Indian Constitution, the Council of Ministers is collectively responsible to the House of the People (Lok Sabha). This means that if a no-confidence motion is passed by a majority of members in the Lok Sabha, the entire Council of Ministers, including the Prime Minister, must resign. This mechanism ensures that the executive remains accountable to the directly elected representatives of the people. - **Option B (Rajya Sabha):** The Rajya Sabha (Council of States) does not possess the power to pass a no-confidence motion against the Council of Ministers. While it can debate and criticize government policies, it cannot directly remove the government from power through such a motion, as the executive is not responsible to it in the same way. - **Option C (Both the Houses separately):** This is incorrect. The power to express no-confidence and compel the government's resignation is vested solely in the Lok Sabha, not in both houses acting independently. - **Option D (Both the Houses in Joint Sitting):** A joint sitting of both Houses is typically convened to resolve legislative deadlocks on ordinary bills, not for a no-confidence motion. The procedure for a no-confidence motion is specific to the Lok Sabha.