[解析]
(1)B.细节理解题.根据文章第一段.He seemed most unfriendly and not at all concerned about my intended purchase.可知服务员对他表现并不热情;故选B.
(2)A.细节理解题.根据第二段.I gave in immediately.The power of that broad smile dissolved all bitterness within me,and I felt the muscles in my own face happily responding.可知,作者看到这个年轻人的笑脸时,自己心里的不快和郁闷也消逝了,他也感到高兴起来了,脸上露出了笑脸;故选A.
(3)C.细节理解题.根据文章最后一段:I shall never forget the lesson he taught me that morning.作者很感激那位再未谋面的人,作者感激他,那天给自己上了一堂珍贵的课,使作者变成了一个在潜意识里爱笑,对人生充满乐观的人;故选C.
(4)D.最推理判断题.根据文章最后一段"From that day on,I became smile﹣conscious,and I practice the art diligently anywhere and everywhere,with everybody",作者体会到了笑的威力之大,决定以后也会对别人多微笑.故选D.