单项选择题

I" m in the unusual position of being both a computer scientist and a professional musician. On the computer side, I" m best known for my work in virtual reality, a term I coined in the early 1980s. As a musician I write, perform, and record my own work. Canons for Wroclaw, a concerto I created for virtual instruments, was performed last December by the Chamber Orchestra of Wroclaw, Poland. All of this means that I have a few deeply felt ideas about Napster, the free software millions of people use to share their music collections over the Internet. Big media companies see Napster as theft because they can" t collect royalties when people use it. So they have asked the courts to kill it. As I write this, a settlement seems to be emerging. Napster will probably begin to charge for its services and pay royalties to at least some record companies. Whatever happens, the legal decisions surrounding Napster are important for reasons that transcend the music business and extend to our basic concepts of what it means to be free in a democracy. I believe the anti-Napster forces have failed to foresee dangerous implications of their course of action. They aren" t thinking about the harsh logic at the core of this technology. They do not understand what I call the Law of the Excluded Digital Middle; Digital tools can be either open or closed but resist being anything in between. An open digital tool is one that can be used in unforeseen ways. A tool like e-mail, meant to send text, might also—surprisingly—be used to send music. A closed tool is one in which there are technical restrictions that prevent unforeseen uses. The advantage of open tools is that more people can create new things with them; consequently, they tend to be more innovative. Closed tools are usually created because it is thought they will be more profitable; An owner can control them well enough to enforce bill collection. Of course, the open software movement energetically promotes the idea that innovation ends up generating more money than control does. The designer of an open digital tool hardly knows______.

A.the risks it may encounter
B.the potential ways of its usage
C.the number of its users
D.the amount of its net profit
热门 试题

问答题
Read the following article in Chinese, and then write a summary of 200 words in English on the ANSWER SHEET. Make sure that you cover all the major points of the article. 如何保持充沛的精力 现代社会生活节奏日益加快,竞争日趋激烈,面对工作上的挑战,生活上的各种压力,许多人都有过在一段时间内情绪低落、容易疲劳、不愿运动、失眠、头痛、注意力不集中等经历,有的甚至长期或经常出现这种情况。因此,怎样才能长时间精力充沛地工作和轻松自如地生活越来越被人们所重视和关注,一些著名的医学和健康专家对这种现代人的通病进行了研究,提出了一系列简便可行的办法。 及时补充能量 在正常的一日三餐之外,每隔2—3小时少量进餐、目的是使血糖维持在能保证满足身体能量需求的水平。从生理上讲,血糖代谢是人体能量的主要来源。因此,不断补充血糖是保持精力充沛的前提,过度节食者难免精疲力尽。所以选择食物时应选择富含碳水化合物(carbohydrate),同时有适量的纤维素(cellulose)和少量的脂肪的食物。 试试香味提神 实验表明吸人含有薄荷(mint)和百花香味(fragrance)的气体能使计算机操作人员明显减少操作失误。具体选择哪种香味并无特殊限制。只要是你喜欢,能带来愉悦感觉的气味都有助于提高大脑的觉醒程度。 补充维生素和矿物质 虽然维生素和矿物质(mineral substances)不具有立竿见影的提神醒脑功效,但他们却是机体正常新陈代谢不可缺乏的营养物质,其中B族维生素、镁(magnesium)、铁尤其重要。医学调查发现相当部分的妇女缺乏某些种类的维生素和矿物质。每日可服用复合维生素药物,但注意不能超过人体实际需要量。 健身锻炼 定期锻炼的最大受益者是你的心脏,故有“完美的体型意味着完美的心脏”之说。此外积极的锻炼能够提高机体产能的效率。当快节奏、高强度的工作需要你付出更大能量时,健康的身体能够游刃有余地释放潜能。现在,城市空气污染严重,对人体危害不浅。在假期和周末远离喧嚣的都市,每隔一段时间到林木茂盛的风景区踏青,可以令人体吐故纳新、调和呼吸、阴阳协调。在绿色植物密集的公园、森林,空气里的负离子(anion)浓度较高。在负离子充沛的地方,人们感到心旷神怡、精神振奋。空气中的负离子不仅能调节神经系统,而且可以促进胃肠消化、加深肺部的呼吸。深呼吸不仅可以摄取更多的氧气,同时能刺激副交感神经(parasympathetic nerve)系统,有助于放松。深呼吸时可以躺下或端坐。一只手放于体侧,另一只手放于腹部,用鼻子吸气,同时排除杂念,想象胸部充分扩展、肺内正充满氧气,然后感觉二氧化碳从体内排出,同时颈肩放松。每次不少于3-5分钟。