Questions 15 to 17 are based on the following passage.
At the end of the passage, you will be given 15 seconds to answer the
questions. Now, listen to the passage. What suggestions did the experts offer to stereo manufacturers
A．Providing a warning light when the sound is too loud. B．Improving the quality of personal stereo systems. C．Standard heating test should be set up. D．Restricting the use of personal systems.