语法填空 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 61 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 62 (poor) studied; however, biologists calculate that there are about 20,000-25,000 polar bears worldwide. Modern methods 63 tracking polar bear populations have been employed only since the mid-1980s, and are expensive 64 (perform) consistently over a large area. In recent years some Inuit people in Nunavut 65 (report) increases in bear sightings around human settlements, leading to a 66 (believe) that populations are increasing. Scientists have responded by 67 (note) that hungry bears may be congregating ( 聚集 ) around human settlements, leading to the illusion ( 错觉 ) that populations are 68 (high) than they actually are. Of 69 nineteen recognized polar bear subpopulations, three are declining, six 70 (be) stable, one is increasing, and nine lack enough data.