If you call yourself a Grammar Snob, you need to try and pass this test from the 1980s. Its reportedly SO hard, nobody can score over 50%.
Try it yourself. Write down or think of your answers, and then check them on the bottom of this article.
ANSWERS
1. Were
2. Is
3. Whom
4. Whose
5. Stay
6. Couldn't
7. Calendar
8. Affected
9. Break
10. Loose
11. Lie
12. Stationary
13. Foreword
14. Is
15. Fulfill
16. Envelope
17. Than
18. Compliment
19. Breach
20. Cemetery