Section B Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice. Nowadays, no document is safe any more. Counterfeiting. once the domain of skilled deceivers that used expensive engraving and printing equipment, has gone mainstream since the price of desktop publishing systems has dropped. In ancient times, counterfeiting was a hanging offence. Today, desktop counterfeiters have little reason to worry about prison, because the systems they use are ubiquitous (普遍存在的) and there is no means of tracing forged documents to the machine that produced them. This, however, may soon change thanks to technology development by George Chiu, an anti-counterfeiting engineer. His approach is based on detecting imperfections in the print quality of documents. Old-school scientists were able to trace documents to particular typewriters based on quirks (构槽) of the individual keys. He employs a similar approach, exploiting the fact that the rotating (转动) drums and mirrors inside a printer are imperfect pieces of engineering which leave unique patterns of banding in their products. Although these patterns are invisible to the naked eye, they can be detected and analyzed by computer programs, and it is these patterns that Dr. Chiu has spent the past year devising. So far, he cannot trace individual printers, but he can tell pretty reliably which make and model of printer was used to create a document. That, however, is only the beginning. While it remains to be seen whether it will be possible to trace a counterfeit document back to its guilty creator on the basis of manufacturing imperfections, Dr. Chiu is now working out ways to make those imperfections deliberate. He wants to modify the printing process so that unique, invisible signatures can be incorporated into each machine produced which would make any document traceable. Ironically, it was after years of collaborating with printing companies to reduce banding and thus increase the quality of prints, that he came up with the idea of introducing artificial banding that could encode identification information into a document. Using the banding patterns of printers to secure documents would be both cheap to implement and hard, if not impossible, for those without. specialist knowledge and hardware to evade. Not surprising, the American Secret Service is monitoring the progress of this research very closely, and is providing guidelines to help Dr. Chiu to travel in what the service thinks is the right direction, which is fine for catching criminals. But how the legitimate users of printers will react to Big Brother being able to track any document back to his source remains to be seen. By saying no document is safe any more, the author probably means _____.