If the regulation of computer networks is to be modeled on past legislation, then its model must be either legislation regulating a telephone system or else legislation regulating a public broadcasting service. If the telephone model is used, computer networks will be held responsible only for ensuring that messages get transmitted. If the public broadcast model is used, computer networks will additionally be responsible for the content of those messages. Yet a computer network serves both these sorts of functions: it can serve as a private message service or as a publicly accessible information service. Thus neither of these models can be appropriate for computer networks. The passage is structured to lead to which one of the following conclusions? ['Regulation of computer networks is required in order to ensure the privacy of the messages transmitted through such networks.', 'Legislators who do not have extensive experience with computers should not attempt to write legislation regulating computer networks.', 'The regulation of computer networks should not be modeled on any single piece of past legislation.', 'A computer network merely duplicates the functions of a telephone system and a television network.']