Final answer:
The underlined word is 'us' and it functions as an indefinite pronoun.
Step-by-step explanation:
The underlined word in the sentence is 'us'.
'Us' is an indefinite pronoun.
Indefinite pronouns are pronouns that do not refer to a specific person or thing. They are used when the speaker or writer does not know or does not want to say exactly who or what is being referred to.
Learn more about Parts of Speech