The correct answer is option 4, a resolution passed by the Lok Sabha. The Speaker of the Lok Sabha can be removed from office if the majority of the members of the Lok Sabha pass a resolution for his removal. This means that the members of the Lok Sabha, who are elected representatives, have the power to remove the Speaker through a resolution. It is important to note that the President, Prime Minister, or both Houses of Parliament do not have the authority to directly remove the Speaker. The resolution passed by the Lok Sabha must have the support of a majority of its members to be successful in removing the Speaker from office.