Final answer:
The phrase 'of course' is used as an adverbial phrase to emphasize certainty.
Step-by-step explanation:
The phrase 'of course' is used as an adverbial phrase in this context. Adverbial phrases provide additional information about the verb in a sentence. In this case, 'of course' is used to emphasize the speaker's certainty about the statement being made. Example: 'He is, of course, a liar.'
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