[单选题]
A polar bear starts at the North Poleby8rbc5 mq *2v,0j 9,uz hnbhz. It travels 1.0 km south, the6,vl 4e6davb1q 5 vimsn 1.0 km east, then 1.0 km north, then 1.0 km west to return to its starting point. This trip takes 45 min. What was the bear's average velocitvm,ql1bv654d ae v6 siy?
