Man paddling a boat on a river near the bank .
It is impossible that a boat is being driven by geese who are too tired to fly south on their own wings .
It is impossible that a boat is being driven by geese who are too tired to fly south on their own wings .
It is probably the case that a boat is being driven by geese who are too tired to fly south on their own wings .
A boat is being driven by geese who are too tired to fly south on their own wings .