The correct answer to the question is option 3 - Sir Pethic Lawrence. The Cabinet Mission was a group of British politicians who came to India in 1946 to discuss and negotiate the terms of India`s independence. The mission was led by Sir Pethic Lawrence, who was the Secretary of State for India at the time. Lord Linlithgow, option 1, was the Viceroy of India from 1936 to 1943, but he did not lead the Cabinet Mission. Lord Mountbatten, option 2, was the last Viceroy of India, but he was not directly involved with the Cabinet Mission. Option 4, Sir Mountford, is not a known person in relation to the Cabinet Mission. Therefore, the correct answer is option 3 - Sir Pethic Lawrence.