质粒是基因工程中最常用的载体,下列关于质粒的叙述,错误的是( ) A .质粒是具有自我复制能力的双链环状的 DNA 分子 B .质粒存在于细菌拟核之中,与拟核一起控制细菌的生命活动 C .作为载体的质粒上有限制酶的切割位点 D .作为载体的质粒存在特殊的标记基因
A. A B. B C. C D. D
点击查看答案
Passage Two Focus on what you do best. This age-old strategy has worked well for RealNetworks, Microsoft’s main competitor in multimedia software for the Internet. Now, the smaller Seattle-based firm is trying a novel way to contain the software giant. On October 29th, it released the underlying recipe, or source-code, of its RealPlayer software and will soon do the same for its other programs — giving away a big chunk of its intellectual property. This may sound like a desperate echo of 1998, when Netscape, struggling in Microsoft’s choke holding, published the source-code of its web browser (an initiative that yielded few real results until this June, when the first serious new version of the open-source browser, Mozilla, was released). Yet RealNetworks is not playing defense. It is trying to encourage the creation of a common multimedia software structure for every kind of file format and device, thus defeating Microsoft’s ambitions in this promising market. The firm hopes that others in the industry (volunteer programmers, media firms and hardware makers) will take the code, called Helix DNA, improve it and make it run on new devices, such as mobile phones and home stereos, turning RealNetworks’ software into an industry standard. Clever licensing terms are supposed to ensure that this standard does not split and that the firm still makes money. Individual developers, universities and other non-profit organizations can modify the software as they please, and even redistribute it for free, so long as they also publish the source-code for their changes. This is a sort of payment in kind, for RealNetworks is then allowed to use these contributions. Firms, on the other hand, must pay royalty fees if they distribute more than lm copies of the code. They also have to make sure that their software works with other Helix DNA products. The software’s development community already has 2,000 members. And several hardware makers hack the effort. But there are risks. Afraid of piracy (盗版), media groups are suspicious of anything that might be related to hackers (although they also do not want to depend on, and pay for, technology controlled by Microsoft). The self-created competition could also hurt RealNetworks if customers decide its commercial products, which will ha based on the open source-cede but with extra features, are not worth paying extra for. RealNetworks’ move is another sign that the software industry is going hybrid. Mixing elements of proprietary software, where the source-code is tightly controlled, with open-source programs enables firms to expand a market, harvest the ideas of others and, they hope, still make money. Even Microsoft is edging this way: it recently announced that partners can now look at — but not modify or re-use — the source-code for Passport, its controversial digital-identity service.
A．RealNetworks makes profit through clever licensing terms.B．RealNetworks intends to cooperate with Netscape to compete against Microsoft.C．Microsoft completely beat Netscape in marketing competition.D．Microsoft has developed a new program superior to that of RealNetworks.
点击查看答案
在编制 " 总分类账户发生额及余额试算平衡表 " 中,若出现三对平衡数字,则 (1.0分)
A. 全部总账账户记录一定正确 B. 全部总账账户记录也不能认为肯定无错 C. 全部明细分类账户记录一定正确 D. 全部明细分类账户记录也不能认为肯定无错
点击查看答案
题目内容
（请给出正确答案）
参考答案
十点题库官方参考答案
（由十点题库聘请的专业题库老师提供的解答）
