如图，△ABC中，∠ACB=90°，CD⊥AB于D，AC=5，BC=12，求CD的长．

《2014年第四季度中国货币政策执行报告》称，人民币中间价全年贬值0．36%，而国际清算银行称人民币实际有效汇率升值了6．24%。人民币实际有效汇率的变化对中国经济的积极影响有（    ）

①提高中国企业或居民的国际购买力②提高中国的国际金融地位，降低中国的国际金融风险③提升中国外向型企业的国际竞争力，增加出口和对外投资④降低我国先进技术、设备的引进成本，积极利用全球化优势

    In the future，life will be much ____. Maybe there will be vision phones in every ____. People can have a medical examination without a ____ or nurse in the room and do some shopping without ____their homes. And what ____education? There will be ____educational programs on the radio or TV. So many children who live in far-away villages don't need to ____to school every day. They can study at home. Each family has a robot. Robots will ____ people do their housework. Perhaps some people will fly to the ____for a holiday and some people can live under the ____.