1. We haven't just received the SOS signal from an unknown ship. Have we just received the SOS signal from an unknown ship?2. The sailors haven't scrubbed the deck lately. Have the sailors scrubbed the deck lately?3. The ice-breaker hasn't already conducted the cargo ship Gotland to the port. Has the ice-breaker already conducted the cargo ship Gotland to the port? 4. They haven't visited the Kremlin today. Have they visited the Kremlin today? 5. We haven't studied how to navigate sailing boats. Have we studied how to navigate sailing boats?