Put the sentences into right order. 根据课文把下列句子按照制作土豆沙拉的正确步骤排序。 ( )1.Wash the potatoes and boil them. ( )2.Cut the sausage, onion and tomato into small pieces. ( )3.Add sugar, salt and onion and mix. ( )4.peel the potatoes and cut them into small pieces . ( )5.Boil the eggs, take the shell off and cut them into pieces. ( )6.It is ready to serve. ( )7.Put the eggs, sausage, potatoes and tomato into a big bowl.