根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    Kingfishers (琴鸟) are small beautiful birds. They have blue bodies, and look 1 cute. Fish is 2 favorite food. They don't live 3 the trees. They live in holes (洞) in the riverbank. But kingfishers are in great 4 now. People change (改变) many rivers. The rivers have new riverbanks, 5 kingfishers are losing their 6. People also make many rivers very 7, so there 8 no fish in the river. There isn't 9 food for kingfishers. We must 10 kingfishers.