【单选题】

·You will hear a talk given by, a spokesman of the U.S. InternationalCommunicationDepartment. He talks about a number of privately owned telephone discounter attacking the cartel of national telephone monopolies that keeps the price of international calls high. ·For each question 23—30, mark one letterA,

B、orC、for the correct answer. ·You will hear the recording twice. If you want to ring back, you have to ______.
A、redial the telephone
B、know the free telephone number to a computerized switch in another countryC、find another person to call you back