The correct answer is B. Whom
Explanation:
A pronoun is a word that refers to someone or something and that replaces a noun (word to name a place, a person or object), most common pronouns include the words "I", "they", "she", "he", etc. But, other words such as "their", "ours", "whom" and "who" are considered as pronouns. In the case of the pronouns "who" and "whoever" these are used to replace other subject pronouns (she, he, it); while in the case of the pronoun "whom" it functions as the object of a sentence and because of this it can be preceded by the preposition "of" or "to" and it replaces object pronouns (him, her, them) and in the case of "whose" it refers to possession.
Considering this in the case of the sentence "To ____ did you give your application for a summer job" the correct pronoun is "whom" as in this case the pronoun is the object of the sentence and can be replaced by an object pronoun such as "him, her or them". For example, it is possible to answer I gave my application to them. Also, the pronoun is preceded by the preposition "to" which suggest the only pronoun possible is "whom" as other pronouns are not commonly preceded by prepositions.
