Polar Bears

Polar bears are ___classified___ (elassify) as marine mammals (海洋哺乳动物). They spend most of their___41___ (life) on the sea ice of the Arctic Ocean. They have a lot of body fat that ___42___ (prevent) them from the cold air and water. Considered ___43___ (skil) swimmers, they can swim six miles per hour. Polar bears spend over 50% of their time ___44___ (hunt) for food, but less than 2% of their hunts are___45___ (success). Because they need a large amount of fat to survive, their diet___46___ (main) consists of seals. The total polar bear population is___47___ (divide) into 19 units. Of those, the ___48___ (late) data from scientific research show that there is a high risk of future decrease. Because of continuing loss of their sea ice habitat (栖息地)___49___ (result) from climate change, polar bears were listed as a threatened animal. Therefore, the___50___(protect) of polar bears' habitat needs to be dealt with as soon as possible.