Here the sentence that best uses the last definition of the word lavish is - For his birthday, his friends would lavish him with many gifts.
Answer: C
Explanation
The word 'lavish' in English language is mostly used to describe or modify something.
Therefore the word 'lavish' is used mostly as an adjective.
In the selected sentence from the above options, the word 'lavish' is used to describe an action by the subject, which here is 'the friends'.
Therefore this option stands distinct from the rest as in the rest option the word 'lavish' is used as an adjective.