Mingming is going home with a dog and two lambs. 明明牵着一只狗和两只小羊回家。
　　On the way home, he comes to a river without a bridge. 他们在回家的路上经过一条河，但是河上没有桥。
　　There is only one small boat. And each time he can only carry one dog or one lamb to the other side of the river. 只有一条小船，并且船很小，他每次只能带一只狗或一只小羊过河。
　　He can not let the dog and the lamb alone, or the dog will kill the lamb. 他不能让狗和小羊单独在一起，否则狗会吃掉小羊。
　　提问
　　Would you please help him? How can he carry both the dog and lamb to the other side of the river safely? 你能帮他想想办法，把狗和小羊都带安全带过河吗？
　　keys
　　先把狗带到对岸，然后返回，把一只小羊带过去，顺便把狗带回原岸，把另一只小样带到对岸。然后再返回，把狗带到对岸去。