Who/Whom

1. (Who/Whom) did you go to the game with?

Whom
2. She’s the student (who/whom) writes the best articles.
Who
3. (Who/Whom) did you vote for?
Whom
4. (Who/Whom) failed the quiz?
Who
5. We know (who/whom) pulled that prank.
Who
6. We want to know on (who/whom) the prank was pulled.
Whom