1. 极光：polar distribution 极角分布 | polar light 极光 | polar molecule 有极分子,极性分子
2. 极光,偏光：polar indication ==> 极性指示 | polar light ==> 极光,偏光 | polar line and plane ==> 极线和极面
1. Polar bears have clear hair shafts that appear white because they reflect light.