单选题
When an invention is made, the inventor has three possible 61 of action open to him; he can give the invention to the world by publishing it, keep the idea 62 , or patent it. A 63 patent is the result of a bargain 64 between an inventor and the state, but the inventor gets a limited period of monopoly and publishes full details of his invention to the public after that period 65 . Only the most exceptional circumstances 66 the lifespan of a patent 67 to alter this normal process of events. The longest extension ever 68 was to Georges Valensi; his 1939 patent for color TV receiver circuit was extended until 1971 because for most of the patent's normal life there was no color TV to 69 and thus no hope for reward for the invention. Because a patent remains permanently 70 after it has terminated, the shelves of the library attached to the 71 office contain details of literally millions of ideas that are free for anyone to use and, if 72 than half a century, sometimes even re-patent. Indeed, patent experts often advise anyone 73 to avoid the high cost of conducting a search through 74 patents that the one sure way of violation of any other inventor's fight is to plagiarize a dead patent. Likewise, because publication of an idea in any other form 75 invalidates further patents on that idea. It is traditionally 76 to take ideas from other areas of print. Much modem technological advance is 77 on these presumptions of legal security. Anyone closely 78 in patents and inventions soon learns that most "new" ideas are, in fact, as old as the hills. It is their reduction to commercial practice, either through necessity or dedication, or through the availability of new technology, 79 makes news and money. The basic patent for the theory for magnetic recording dates back to 1886. Many of the original ideas behind television originate 80 the late 19th and early 20th century. Even the Volkswagen rear engine car was anticipated by a 1904 patent for a cart with the horse at the rear.