He said that he had done the work'. The direct speech is

In indirect speech, past perfect ('had done') usually comes from past indefinite ('did') or present perfect ('have done'). Given the subject 'he' in direct speech referring to the speaker, the most appropriate direct form is: He said, 'He did the work' (referring to a third person) or if he referred to himself, 'I did the work'. Based on the options, option 4 maintains the tense transformation logic correctly.