题目

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。 We find different kinds of animals in the world. Some animals, such as tigers and lions, live in big forests and they are called 1 animals. Some others like sheep and dogs are2by men and they are called domestic animals (家养动物). These animals are very different from one another, but we can 3 them into big groups: those that eat other animals and those that eat grass and leaves. Animals like the4belong to the first group. Animals are 5 great use to human beings. Men6 wild animals for their 7如图△ABC为等边三角形，直线a∥AB，D为直线BC上一点，∠ADE交直线a于点E，且∠ADE=60°．（1）若D在BC上（如图1）求证CD+CE=CA；（2）若D在CB延长线上，CD、CE、CA存在怎样数量关系，给出你的结论并证明．