who v. whom

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

 whom

2. She’s the student (who/whom) writes the best articles.

 whom

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