[单选题]
A polar bear starts at ty59voi 2bb fqnk9u-5u 7lzqlev 7g: j,he North Pole. It trave4i m4knbv: o+ols 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km west to return to its starting point. Thbvoi 4o+4m:n kis trip takes 45 min. What was the bear's average velocity?
