Questions 11 to 13 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’s the main point the speaker makes

A．Content of speech is more important than tone of voices.
B．Voice quality has a strong effect on listeners.
C．Effective speakers must use visual aids.
D．Amplifying devices are essential in large rooms.