Some government economists view their home countries as immune to outside influence. But economies are always open systems; international trade significantly affects prices and wages. Just as physicists learned the shortcomings of a mechanics based on idealizations such as the postulation of perfectly frictionless bodies, government economists must look beyond national borders if their nations' economies are to prosper. The argument's conclusion follows logically if which one of the following is assumed? ['Some government economists have been ignoring the effects of international trade on prices and wages.', 'Economic theories relying on idealizations are generally less accurate than economic theories that do not rely on idealizations.', "A national economy cannot prosper unless every significant influence on it has been examined by that nation's government economists.", 'Economics is weakly analogous to the physical sciences.']