Answer:
All
Explanation:
An indefinite pronoun is a pronoun that does not refer to any person, amount, or thing in particular.
"If" is not a pronoun, usually working as a conjunction instead.
"They" is a pronoun, but refers specifically to either one person or to a group a people, so it is not indefinite.
"Ours" is also a pronoun, but refers specifically to the speaker and previously mentioned others, so it is also not indefinite.
"All" is a pronoun which can refer to any amount of people or things. It is not specific, so it is an indefinite pronoun.
