Explanation:

- The Council of Ministers is a critical body in the Indian government, led by the Prime Minister.

- They implement executive decisions, propose legislations, and ensure governance.

- Their collective responsibility is primarily to the Lok Sabha.

- Option 1: Lok Sabha - Correct Answer. The Council of Ministers is collectively responsible to the Lok Sabha. They must maintain the confidence of the Lok Sabha to stay in power.

- Option 2: Parliament - In practice, accountability lies specifically with the Lok Sabha, not the entire Parliament.

- Option 3: Both Lok Sabha and Rajya Sabha - Responsibility is specifically to the Lok Sabha.

- Option 4: President of India - The President appoints the Council but is not their accountability body.