Answer:
"It"
Explanation:
A pronoun is a word that substitutes a specific noun, which is known as the antecedent. Pronouns are words like he, she, it, they, them, etc.
The only pronoun here is "it" at the beginning of the sentence. However, notice that there is no antecedent, or noun, that comes before it. Because there is nothing prior to "it", we cannot guess what "it" is talking about, making it the vague pronoun.
Hope this helps!
