The infinitive in this sentence is the singer and it is working as adverb. Thus the option (C) is correct.
What is Adverb?
Adverb refers to those words which adds something to the meaning of the verb. It gives the extra knowledge about the verb. For example: Johan walks slowly. In this sentence the verb is walk and slowly is the adverb.
Thus in the above sentence, to watch is the infinitive and it is working as adverb. Infinitives are the base form of the verb with takes "to" before them. Thus watch is the base form of verb and it takes "to" before it.
Thus the option (C) is correct.
Learn more about verbs here:
https://brainly.com/question/14574299
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