Answer: Aquellos
Step-by-step explanation:
"Aquellos" in this sentence is a masculine, demonstrative adjective in the plural, that agrees in gender and number with the noun it accompanies and can replace it in a sentence when it functions as a pronoun.
Aquellos bolivianos => "Aquellos" here is a demonstrative pronoun, because it does not accompany the noun, but replaces it.
