阅读短文，根据上下文内容选词填空。

 swan   warm ducklings  back  cold into  ugly  swim

    In spring, itis sunny and ____.Mother Duck has four ____. But she is surprised(惊讶的). Because three ducklings are small and yellow. The last oneis big and grey. It's ____. The ugly duckling is very sad. His three brothers can sit on their mother's ____.But he can't. He ____away. In winter, it is ____.The ugly duckling has no home. The ugly duckling grows and grows. It is spring again.The ugly duckling looks ____ the water. How beautiful! He is big and white now. He is a beautiful ____! He is very happy.