分子和原子的本质区别是（   ）

阅读《送东阳马生序（节选）》，完成小题。
       余幼时即嗜学。家贫，无从致书以观，每假借于藏书之家，手自笔录，计日以还。天大寒，砚冰坚，手指不可屈伸，弗之怠。录毕，走送之，不敢稍逾约。以是人多以书假余，余因得遍观群书。既加冠，益慕圣贤之道。又患无硕师名人与游，尝趋百里外，从乡之先达执经叩问。先达德隆望尊，门人弟子填其室，未尝稍降辞色。余立侍左右，援疑质理，俯身倾耳以请；或遇其叱咄，色愈恭，礼愈至，不敢出一言以复；俟其欣悦，则又请焉。故余虽愚，卒获有所闻。
       当余之从师也，负箧曳屣行深山巨谷中。穷冬烈风，大雪深数尺，足肤皲裂而不知，至舍，四支僵劲不能动，媵人持汤沃灌，以衾拥覆，久而乃和。寓逆旅，主人日再食，无鲜肥滋味之享。同舍生皆被绮绣，戴朱缨宝饰之帽，腰白玉之环，左佩刀，右备容臭，烨然若神人；余则缊袍敝衣处其间，略无慕艳意，以中有足乐者，不知口体之奉不若人也。盖余之勤且艰若此。

    A well-dressed man goes into a restaurant one day. He sits down at a table near the window. A waiter comes up to him and says, “Can I help you, sir?”

    The man says, “Can I see the menu?” “Certainly.”

    The man wants a good meal and he wants a lot of nice dishes. The waiter gets them for him. The man is having his meals. At this time, a boy comes in and sits beside the man. He asks the man to give him an ice cream. The man does so.

    Now the boy is eating his ice cream. The man says, “I go out for a newspaper.” The man goes out.  After the boy eats his ice cream up, he stands up and goes to the door.

    “Excuse me. Your father doesn't give the money for the meal and your ice cream,” The waiter stops him and says.

    “Father? You are wrong. He isn't my father. I don't know him. I meet him in the street. He says he will give me an ice cream if I come here at 12 o'clock.”