You may get hungry on the train , so take some sandwiches(in case) => The postman was bitten by out dog(bit) => My husband didn't leave the car key,so i couldn't pick him up the station(if) =>

You may get hungry on the train, so take some sandwiches(in case)
=> In case you may get hungry on the train, you should take some sandwiches.
The postman was bitten by out dog(bit)
=>  Our dog bit the postman.
My husband didn't leave the car key,so i couldn't pick him up the station(if)
=> If my husband had left the car key, I could have picked him up the station.

#NOCOPY