Answer:
with whom you can discuss this plan
Explanation:
An adjective clause is a group of related words with a verb and a subject that does not express a complete thought (they're dependent clauses) and whose function is to modify nouns. Very often, these type of clauses begin with a relative pronoun, namely, who, whom, whose, that or which, or a relative adverb like when, where or why.
In the sentence, then, the complete adjective clause is “with whom you can discuss this plan” because it is a dependent clause (it does not express a complete thought on its own and has a subject and a verb) and its function is to modify or describe the noun “Dad.”
