Accusative Case is used to show the direct object of the verb.
e.g. The cat drank our milk
drank – verb
our milk - the accusative case (question to be asked – drank what?)
some times preposition take the accusative case form or they are sometimes the object of preposition. e.g. him and whom.
In the sentence “My aunt, with ______ we went shopping, took us to dinner”
whom is correct answer.
Here whom is the object of the preposition with
B) Who - is used when referring to the subject of the sentence
C) Whose - is used for lifeless things and cannot be used here.
D) Which - is used for animals and lifeless things