Answer: stars
Step-by-step explanation:
A pronoun is a word that is used to replace a noun in a given sentence. Pronouns are used so that one can avoid repeating the nouns in the sentence.
From the question given, "they" is used to replace the stars. In this case, we should note that "they" is a pronoun that's used when there are more than one person or thing. In this case it's referring to the stars.