1. The polar bear is found in the Arctic Circle and some big land masses as far south as Newfoundland. While they are rare north of 88°, there is evidence _ they range all the way across the Arctic, and as far south as James Bay in Canada. It is difficult to figure out a global population of polar bears as much of the range has been _ (poor) studied; however, biologists calculate that there are about 20,000 - 25,000 polar bears worldwide. Modern methods _ tracking polar bear populations have been employed only since the mid-1980s, and are expensive _ (perform) consistently over a large area. In recent years some Inuit people in Nunavut _ (report) increases in bear sightings around human settletments, leading to a _ (believe) that population are increasing. Scientists have responded by _ (note) that hungry bears may be congregating（聚集）around human settlements, leading to the illusion（错觉） that populations are _ (high) than they actually are. Of _ nineteen recognized polar bear subpopulations, three are declining, six _ (be) stable, one is increasing, and nine lack enough data.