若|m-3|+（n+1）²=0，则2m-n的值是(         )

阅读下文，回答问题

医药费——满满一大杯牛奶

    一个出身贫苦的男孩，为了积攒学费而挨家挨户地推销商品。

    他奔走了一整天，到傍晚时又累又饿，可身上只剩下一毛钱。他决定向下一户人家讨一口饭吃。可是，当一个天使似的姑娘打开大门时，他却有点不知所措了。他不好意思张口要饭吃，只求姑娘给他一口水喝。姑娘看出他的疲惫和饥饿，微笑着给了他满满一大杯牛奶。男孩饥不择食地喝完牛奶，嗫嚅地说：“我应该付您多少钱？”姑娘仍旧微笑着对他说：“您不用付钱，妈妈经常教导我们：施以爱心，不图回报。”泪水涌上了男孩的眼眶，他轻轻地说：“那么，就请你接受我由衷的感谢吧！”其实，男孩本来打算退学的，如今，他仿佛看到上帝在朝他点头微笑，他觉得浑身有劲，男子汉的豪气又迸发出来了。

    若干年之后，有一个来自小镇的姑娘得了一种罕见的重病。当地医生束手无策，只好把她送到大城市去，请专家们会诊治疗。一位有名的医生参加了会诊。他看到病历上记载的家庭地址，马上直奔病房。来到病床前，他一眼就认出了这个病人就是当年送过满满一大杯牛奶给他喝的天使。他回到办公室，决心竭尽所能回报这个“施以爱心，不图回报”的姑娘。经过艰辛努力，手术成功了，姑娘渐渐康复。这位医生要求医院把账单送到他的办公室，他付清了一切费用，并微笑着签上自己的名字。姑娘坚持要知道她应支付多少医药费。可是，当账单送到她手上时，她又不敢看，因为她确信：这笔费用将花去她所有的积蓄，或许，还不够。最后，她还是鼓起勇气，颤抖着翻开了这沓厚厚的账单。末尾的签字吸引了她的目光，她不禁轻声读了出来：“医药费——满满一大杯牛奶。霍华德•凯利医生。”

    Not everyone has the chance to be a detective. But I ever got one when I was thirteen years old. It happened in 1988.

    One afternoon, I was walking down the street when I saw my 1 new car. I expected to see my father, but to my 2 , I saw a young woman driving instead. “She stole my father's car,” I thought. So I quickly stopped a 3  and got in. I said to the driver, “Follow that new car 4 . ” And I told him why.

    The taxi driver had a car telephone, and I asked him to 5  the police. Soon we heard the 6  of a police car and its loudspeaker. The policeman told the woman to 7  her car. Our car came to a stop, too. I 8  right then and said to the woman, “It's not 9  car. It's my father's.”

    The woman 10  and said, “Oh. You're Mr Jackson's son, right? I've once seen your photo at your father's 11 .”

    Before I could say 12  word, the woman explained that she was my father's new assistant. My father had asked her to take his computer to the shop to have it 13 . He lent her his car. After hearing her words, we called my father and he told us what she said was 14 . the police and the taxi driver laughed. I 15 very sorry. It was both the first time and the last time for me to work as a detective. Don't you think my story funny?