Railroads justify rate discrimination against captive shippers on the grounds that in the long run it reduces everyone's cost. If railroads charged all customers the same average rate， they argue， shippers who have the option of switching to trucks or other forms of transportation would do so， leaving remaining customers to shoulder the cost of keeping up the line. It's a theory to which many economists subscribe， but in practice it often leaves railroads in the position of determining which companies will flourish and which will fail. “Do we really want railroads to be the arbiters of who wins and who loses in the marketplace？” asks Martin Bercovici， a Washington lawyer who frequently represents shippers.
The word “arbiters” most probably refers to those.
［A］ who work as coordinators［B］ who function as judges
［C］ who supervise transactions［D］ who determine the price［2003年54题］
For any job search， you should start with a narrow concept—what you think you want to do—then broaden it. “None of these programs do that，” says another expert. “There's no career counseling implicit in all of this.” Instead， the best strategy is to use the agent as a kind of tip service to keep abreast of jobs in a particular database； when you get E_mail， consider it a reminder to check the database again. “I would not rely on agents for finding everything that is added to a database that might interest me，” says the author of a job_searching guide.
The expression “tip service” most probably means .
［A］ advisory［B］ compensation
［C］ interaction［D］ reminder［2004年43题］