完形填空
阅读下面短文，掌握其大意， 然后从21-40各题所给的四个选项（A、B、C和D）中，
选出最佳选项。
It was the old lady’s birthday. She got up early to be ready for the post. From the second floor flat she could see the postman when he came down the street，and a little boy，Johnnie，__1__her letters from the ground floor on the rare__2__when anything came.
