单项选择题

Today, the world wide web can be used both to (31) information and to make it (32) to others. Information (33) on webpages is viewed (34) means of browser. The sources of information linked in this way can be located on any computer (35) is also part of the web. Each information source (36) to an indefinite number of other webpages. Hypertext and hyperlinks allow users acting as receivers of information to (37) from one source of information to (38) , (39) for themselves which information they wish to (40) to their browser and which links they want to (41) .
The addresses of webpages can be found by using the many hundreds of general and specialized search engines which provide (42) to databases which hold information on them. Once a webpage has been found, hyperlinks may point (43) other places of interest on the web. Addresses of webpages also (44) in other more conventional media, such as magazines, newspapers and television programs, and on posters. Webpages, in their (45) , facilitate access to information made available by other (46) of media, for example, collections held in libraries or programs broadcast on television.
Most webpages offer interactive opportunities which go (47) merely allowing visitors freedom as to when and how they visit a page and where they might choose to go next. Feedback can be kept formal via a questionnaire which can be filled (48) , or (49) by providing an address for e-mail or even by installing a digital guest book for comments left for other users to read. Although all webpages are protected (50) unauthorized visitors cannot make unsolicited changes to them, it is also possible to limit access to pages on the Internet to those holding a password.