indicate whom among us is ignorant of Polish.
You are getting worse by the minute, professor.
"Whom"? Are you serious or just testing me? No, professor, it's "who among us is...", not "whom".
Do you know why? It's so because the answer is
he, not
him. For example:
He among us is the tallest.
Getting too professorial with English is a very bad habit that leads to bad places.