Answer:
Who did you visit in Mexico last summer?
Explanation:
In the question above Who, Whoever, Whose, Whom are interrogative pronouns.
Pronouns are words we use to substitute nouns.
who, whoever are subject pronouns. They work in accordance with the verb because subject pronouns refer to the person or things performing the verb. I, we, he, she, they.
Whom is an object pronoun. They receive the actions of the verb. They work along side verbs and prepositions. me, him, her, them.
Whose used to denote possessions of people.
- Who is used for people. Directed towards the person visited.
- Whoever means - the person or people who / any person who.
Who is most appropriate.