Final answer:
The sentence uses the Present Perfect tense to show an action that started in the past and continues into the present or is just completed.
Explanation:
Present Perfect tense is used in the given sentence: 'You have done me a great favour.'
The present perfect tense is formed by combining the auxiliary 'have' with the past participle of the main verb. It is used to indicate actions that started in the past and continue into the present or have just been completed.
Examples in the sentence include 'have done,' where 'have' is the auxiliary verb and 'done' is the past participle, indicating an action that occurred in the past and has present relevance.
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