文章介绍了在圣诞节前夕，一位老师和学生之间发生的事情。学生亲手制作的圣诞礼物深深地感动了老师。
16．B 考查语境。根据上文By the third year of teaching I'd begun to expect Christmas break more for the school holiday and less for the excitement of the children可知，教学使得作者很疲劳。此处表示“我很疲劳”，故选B。
17．D 考查语境。根据下文through the cold into the overly heated school building可知，heavily此处表示“我迎着寒风艰难地走进教学楼”，故选D。
