1. They must live in St. Petersburg.2. They may live in St. Petersburg.3. They might live in St. Petersburg (although it's unlikely).4. They can't live in St. Petersburg.5. They must have lived in St. Petersburg.6. They may have lived in St. Petersburg.7. They might have lived in St. Petersburg (although it's unlikely).8. They can't have lived in St. Petersburg.9. He must be at work.10. He must have been at work.11. He may be at work.12. He may have been at work.13. He might be at work (although it's unlikely).14. He might have been at work (although it's unlikely).15. He can't be at work.16. He can't have been at work.