在研究性学习中同学们了解到氢气具有还原性．他们用氢气还原氧化铜的方法测定某氧化铜样品的纯度（杂质不与氢气反应），同学们设计了以下实验装置，准确称取15克干燥样品进行实验．

研究历史离不开文字资料。我国有文字可考的历史开始于（   ）

    For many people who live in cities, parks are an important landscape. They provide a place for people to relax and play sports, as well as a shelter from the often severe environment of a city. What people often overlook is that parks also provide considerable environmental benefits.

    One benefit of parks is that plants absorb carbon dioxide and give off oxygen. According to one study, an acre of trees can absorb the same amount of carbon dioxide that a typical car emits in 11,000 miles of driving. Parks also make cities cooler. Scientists have long noted what is called the Urban Heat Island Effect: building materials such as metal and concrete (混凝土) absorb much more of the sun's heat and release it much more quickly than trees and grass. Because city landscapes contain so much of these building materials, cities are usually warmer than surrounding rural areas. Parks and other green spaces help to lessen the Urban Heat Island Effect.

    Unfortunately, many cities cannot easily create more parks. However, cities could benefit from many of the positive effects of parks by encouraging citizens to create another type of green space: rooftop gardens. While most people would not think of starting a garden on their roof, human beings have been planting gardens on rooftops for thousands of years. Some rooftop gardens are simple container gardens that anyone can create with the investment (投资) of a few hundred dollars and a few hours of work.

    Rooftop gardens provide many of the same benefits as other urban parks and garden spaces, but without taking up the much-needed land. In the summer, rooftop gardens prevent buildings from absorbing heat from the sun, which can significantly reduce cooling bills. In the winter, gardens help control the heat that materials like brick and concrete release so quickly, leading to savings on heating bills. Rooftop vegetables and herb gardens can also provide fresh food for city settlers, making their diets healthier. Rooftop gardens are not only something everyone can enjoy but also a smart environmental investment.

阅读下文，回答问题

读书人是世间的幸福人

    我常想，读书人是世间的幸福人，因为他除了拥有现实的世界之外，还拥有另一个更为浩瀚也更为丰富的世界。现实的世界是人人都有的，而后一个世界却为读书人所独有。由此我想，那些失去阅读机会或不能阅读的人是多么的不幸，他们的损失是不可补偿的。世间有诸多的不平等，如财富的不平等，权力的不平等，而阅读能力的有无却体现为精神的不平等。

    人们通过阅读，可以进入不同时空的诸多他人的世界。这样，具有阅读能力的人，无形中就获得了超越有限生命的无限可能性；阅读不仅使他认识了草木虫鱼之名，而且使他上溯远古下及未来，饱览存在的与非存在的奇风异俗。

    更为重要的是，读书加惠于人们的不仅是知识的增长，而且，还在于精神的感化与陶冶。人们从书中学做人，从那些往哲先贤以及当代才俊的著述中学得他人的人格。①人们从《论语》中学得______________，从《史记》中学得___________________，从《正气歌》中学得________________……

    一个人一旦与书本结缘，极大的可能是注定了与崇高追求和高尚情趣相联系。说“极大的可能”，指的是不排除读书人中也有卑鄙和奸诈者；况且，并非凡书皆好，在流传的书籍中，并不全是劝善之作。但我们所指的书是以其优良品质得以流传的一类，这类书对人的影响总是良性的。我之所以常感读书幸福，是从喜爱文学书的亲身感受而发。一旦与此种嗜好结缘，人多半因而向往于崇高，对暴力的厌恶和对弱者的同情，使人心灵纯净而富有正义感。②笛卡尔说：“读一本好书，就是和许多高尚的人谈话。”这就是说，读书使人________；雨果说：“各种蠢事，在每天阅读好书的影响下，仿佛烤在火上一样渐渐熔化。”这就是说，读书使人________；刘向说：“书犹药也，善读之可以医愚。”这就是说读书使人________……

    所以，读书人是世间的幸福人。