D - to serve. This is because the infinitive verb is the form of the verb before it has been conjugated to gain a person (I, you, he/she/it, we, you plural, they) and a tense. In English, such verbs are expressed as 'to ____', and this is how you will see them when you look them up in the dictionary.
I hope this helps
The complete infinitive phrase in the sentence is "to serve the veggie burgers," making option C the correct answer. An infinitive phrase includes the word "to" followed by a verb and can also have its objects. Understanding this structure helps identify infinitive phrases in sentences.
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