完形填空。阅读下面短文，掌握其大意，从每题所给的A、B、C、D四个选项中，选出最佳选项。
Even though it was only October, my students were already whispering about Christmas plans. With each passing day everyone became more anxious, waiting for the final school bell. Upon its 1 everyone would run for their coats and go home, everyone except David
David was a small boy in ragged clothes. I had often wondered what kind of home life David had, and what kind of mother could send her son to school dressed so 2 for the cold winter months, without a coat, boots, or gloves. But something made David 3. I can still remember he was always 4 a smile and willing to help. He always stayed after school to straighten chairs and mop the floor. We never talked much. He 5 just simply smile and ask what else he could do, then thank me for letting him stay and slowly head for home
