Which sentence correctly uses a nominative case pronoun?

a. Them and Alex are eager explorers.

b. The late sleepers are my brother and me.

c. Have him and Ernie finished the obstacle course yet?

d. The neighborhood kids and we waited for the parade.

A nominative case pronoun is a pronoun in its basic form, so: I, you, he/she/it, we, you, they. So, the correct answer is D, 'we' is a nominative case pronoun, that is, it has to be the subject of the sentence.

The other examples have only objective case pronouns: them, me, him - either used incorrectly, or as objects.