It is difficult to figure out a global population of polar bears as much of the range has been poorly studied.
由于大部分有关其生活范围的研究还很少，所以很难统计出全球北极能的数量。
2
Often, scientists see large chunks drifting in polar seas, and then have to work backwards to figure out the point of origin.
通常来说，科学家们都是先观测到极地洋面漂浮着大面积冰块，之后再追溯它原始的形成过程。
3
As the zoo tries to figure out what killed Knut, animal-rights groups are blaming zookeepers for his death, accusing officials of putting financial interests ahead of the famous polar bear's welfare.