Final answer:
The average lead time for tornado warnings is typically 12 minutes before a tornado strikes.
Step-by-step explanation:
The average lead time for tornado warnings is typically 12 minutes (d) before a tornado strikes. Tornado warnings are issued by the National Weather Service (NWS) when there is a high probability of a tornado occurring based on radar and/or eyewitness reports. This lead time allows people to take protective actions and seek shelter, increasing their chances of staying safe during a tornado.