【正确答案】 D

【答案解析】[听力原文] So we've been talking about the printing press—how it changed people's lives, um...making books more accessible to everyone. More books mean more reading, right? But, as you know, not everyone has perfect vision. This increasing literacy, urn, in reading, led to an increasing demand for eye glasses. And this increased demand impacted the social attitudes toward eye glasses. But, first let me back up a bit and talk about vision correction before the printing press. And, urn, what did people with poor vision do before glasses were invented? Well, in some places, the wealthiest people with poor vision could have someone else read to them. Another solution was something called a 'reading stone'. Mound 1000 C.E. European monks would take a piece of clear rock, often quartz, and place it on top of the reading material. The clear rock magnified the letters, making them appear larger. But rocks like quartz, well, quartz of optical quality weren't cheap. Late in the 13th century, glass maker in Italy came up with a less expensive alternative. They made reading stones out of clear glass. And these clear glass reading stones evolved into the eye glasses we know today. So we're pretty sure that glasses were invented in about the late 1200s, well over a hundred years before the printing press. However, it's not clear who exactly invented them first or exactly what year. But record shows that they were invented in both Europe and China at about the same time. By the way, we call this 'independent discovery'. Independent discovery means when something is invented in different parts of the world at the same time and it's not as unusual as it sounds. You can look at the timeline charts in the back of your textbook to see when things were invented in different cultures at about the same time to see what I'm talking about. So now let's tie this to what I said before about social attitudes towards glasses. Initially in parts of Europe and in China, glasses were a symbol of wisdom and intelligence. This is evident in the artwork from the period. European paintings often portrayed doctors or judges wearing glasses. In China, glasses were very expensive. So in addition to intelligence, they also symbolize affluence, um, wealth. In 14th century Chinese portrays the bigger the glasses, the smarter and wealthier this subject was. So glasses were a status symbol in some parts of the world. The invention of the painting press makes books became readily available and more people wanted to read. So the need, well, actually not only the need but the demand for more affordable glasses rose drastically. Eventually, inexpensive glasses were produced, and then glasses were available to everyone. People could purchase them easily as well. According to the professor, what was an advantage of using clear glass instead of quartz to make reading stones? 本录音三道题选项中的clear glass，quartz，inventions，vision correction和correct vision表明，录音可能与某项发明有关，可能涉及使用的材料或视力矫正。选项中重复出现的clear glass，than和quartz，以及easier和less expensive表明，本题可能考查透明玻璃与石英的不同之处。录音中提到，像石英这种具有光学性能的石头比较昂贵，在13世纪末期，意大利玻璃制造商提出一种比较便宜的替代方式，用透明玻璃来制作“阅读石”(reading stones)。由此可知，用透明玻璃代替石英的一个好处就是玻璃的成本更低，故答案为D。