The largest Committee of the Parliament is the Estimates Committee, which is option 2. This committee is responsible for examining the estimates of expenditure presented by the government. It also examines the reports of the Comptroller and Auditor General of India, which provides insights on the financial performance of the government.

Option 1, the Public Accounts Committee, is responsible for examining the audit reports of the government`s accounts. It focuses on ensuring transparency and accountability in the use of public funds. While this committee plays a crucial role, it is not the largest committee.

Option 3, the Committee on Public Undertakings, deals with the examination of the functioning of public sector undertakings. It looks into matters such as the utilization of resources and the efficiency of these undertakings.

Option 4, the Committee on Petitions, considers the petitions received from the public. It examines these petitions and makes recommendations accordingly.

Therefore, the correct answer is option 2, the Estimates Committee, as it is the largest committee of the Parliament, responsible for examining the government`s expenditure estimates.