The correct answer is No improvement. Key Points​​ ​The pronouns that connect a clause or phrase to a noun or a pronoun, is called a relative pronoun. The most common relative pronouns are: who, whom, whose, which, that. Example: We don’t know the person who donated this money. You need to tick the box which says yes.​ ​We use 'who' in relative clauses to refer to people, and sometimes to pet animals. (refer to the above example) We use 'which' in relative clauses to refer to animals and things, to introduce defining and non-defining relative clauses. We use 'whom' if the noun/pronoun is the object of the verb in the dependent clause. Example: The uncle whom we met at the family reunion is coming to visit. (The noun 'uncle' is the object of the verb met.) The person with whom I spoke was able to help me. (The noun 'person' is the object of the preposition with.) ​As per the rule given above, 'whom' will be used in the underlined part of the sentence. ​​​​Additional Information ​ ​​We use 'which' in relative clauses to refer to animals and things. Example: You need to tick the box which says Yes.