1. 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 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 settlements, leading to a (believe) that populations 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.