2 Some people put the letters into boxes for different towns.
3 Some people put postmarks to the letters.
4The postman takes the letters to the sorting office.
5 A machine sorts the letters from the parcels.
6 The letters go to different towns by train.
7 The postman delivers the letters.
По-моему, это не для 3 класса, а проверка работников почтслужбы на профпригодность))