[单选题]
A polar bear starts at the North Pole.fluukjpv28jp+ , 56aj ,t0yhjmyr*2s It travels 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km wj0* m,hyystr2est to return to its starting point. This trip takes 45 min. What was the bear's average velocity?
