Which sentence correctly uses a nominative case pronoun?
a. the girl on the left is her.
b. ralph and them are waiting for us at the metro station.
c. did isaac and him find the missing game controller?
d. the boys were max and i on the trampoline.

The correct answer is B. Ralph and them are waiting for us at the metro station. It is a nominative case pronoun because them is here used as a subject, that is, the doer of the action, so it is nominative. The rest are either objective case or dative because the forms are things like him instead of he which answers the question of to whom instead of who.