原子能

科学家研究发现，原子（atom）由居于中心的原子核和核外电子构成．构成原子各种微粒的电性和质量见下表．原子核体积很小（半径约为10^﹣14m），如果把原子比做一个庞大的运动场，而原子核只相当于一只蚂蚁．

原子核中蕴藏着巨大的能量，原子核的变化（从一种原子核变化成为另一种原子核）往往伴随着能力的释放．目前人们开发核能的方法有两种：一种是重元素的裂变，如铀的裂变；另一种是轻元素的聚变，如氘、氚、锂等．1克铀全部裂变，释放的能量超过2000千克煤完全燃烧时释放的能量．1克氘经过核聚变可能提供相当于10000升汽油完全燃烧后释放出的能量．根据统计，10吨氦﹣3就能提供中国一年所需的能源总量．

请根据上述材料，回答下列问题：

根据短文理解，选择正确答案。

    Frederick was ill and went to the hospital. A doctor looked him over and said, "Well, Mr Green, you're going to get some injections(针), and you'll feel much better. A nurse will come and give you the first this evening, and you'll have to get another one tomorrow evening.'' In the evening a young nurse came to Frederick's bed and said to him. "I'm going to give you your first injection now, Mr Green. Where do you want it?"

    The old man was surprised. He looked at the nurse for a while, then he said, "Nobody has ever let me choose that before. Are you really going to let me choose now?"

    "Yes, Mr Green," the nurse answered. She was in a hurry, "Where do you want it?"

    "Well, then,'' the old man answered with a smile, "l want it in your left arm, please."