Do you know polar bears well? In this article, we will discuss some     14     (amaze) facts about polar bears.

Black skin and white fur. Interestingly, polar bears usually have black skins which     15     (cover) with fur. When you see the white bear, it is because     16     (it) fur is a hollow transparent tube (中空透明管) that only     17     (reflect) light. This feature gives polar bears great advantage in their environment especially when they are hunting.

Polar bears live in cold     18     (place). The natural habitat (栖息地) of polar bears is in the Arctic in Canada, Russia, and so on. While the Arctic is known for extremely freezing temperatures, bears still manage to remain warm thanks       19     the 10 cm thick layers of fat under their skins and their thick furry coats.

Their population. It is estimated (估计) that there are about 20,000 polar bears. Polar bears are used to freezing temperatures. However, because the global temperature is rising, ice on the sea melts a bit     20     (fast) than usual. This way, bears don’t have enough time     21     (hunt) for food, so they are easy to go hungry. Each of the countries     22     bears have their natural habitat follows strict rules on hunting polar bears to prevent them from     23     (face) extinction.