Final answer:
Cuban Ruben is a character mentioned by Yunior in 'The Brief Wondrous Life of Oscar Wao', and he is closely connected to Lola's life, having had a child with her.
Step-by-step explanation:
Cuban Ruben is a character in the novel “The Brief Wondrous Life of Oscar Wao” by Junot Díaz. The question refers to which of the characters in the book he is most closely associated with. The correct answer is c) Yunior's acquaintance; He is referred to by Yunior and is closely connected to Lola's life, having a child with her. Ruben is indeed an important figure to Lola and becomes entangled in her life for a significant period. As an acquaintance of Yunior, he is mentioned and plays a role within the context of Lola's personal journey within the narrative.