第二节：根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Polar bear mothers dig dens in the snow to protect them and their cubs. ____1___ When they are born, the cubs will be about the size of a human adult’s hand.
Polar bears go into a deep winter sleep. ___2___ The cubs may be born and begin nursing while the mom is still in her winter sleep.
Cubs are born blind and without fur. Although they soon grow fur and gain sight, the mother must continue to protect them for about two years.
