Respuesta :

Each of the uncles had lost His invitation. Because we know that everyone being talked about is a male (uncles), we have to use the pronoun "his" as the answer.

Each is a determiner and pronoun used to refer to every one of two or more people or things, however, this is a determiner is singular, according to the rule, pronoun that is singular require singular verbs and pronouns, following the rule the answer would be Each of the uncles had lost his invitation, the option C.