A、To calm themselves down. B、To enhance concentration. C、To show their impatience. D、To signal lack of interest. B选项均为不定式结构，由其中的

While Gail Opp-Kemp, an American artist, was giving a speech on the art of Japanese brush painting to an audience that included visitors from Japan, she was confused to see that many of her Japanese listeners had their eyes closed. Were they turned off because an American had the nerve to instruct Japanese in their own art form? Were they deliberately trying to signal their rejection of her?
    Opp-Kemp later found out that her listeners were not being disrespectful. Japanese listeners sometimes close their eyes to enhance concentration. Her listeners were showing their respect for her by chewing on her words.
    Someday you may be either a speaker or a listener in a situation involving people from other countries or members of a minority group in North America. Learning how different cultures signal respect can help you avoid misunderstandings. Here are some examples:
    In the deaf culture of North America, many listeners show applause not by clapping their hands but by waving them in the air.
    In some cultures, both overseas and in some minority groups in North America, listeners are considered disrespectful if they look directly at the speaker. Respect is shown by looking in the general direction but avoiding direct eye contact.
    In some countries, whistling by listeners is a sign of approval, while in other countries, it is a form of insult.
Questions 19 to 21 are based on the passage you have just heard.
19. What did Opp-Kemp’s speech focus on?
20. Why do Japanese listeners sometimes close their eyes while listening to a speech?
21. What does the speaker try to explain?