A、The player invents the music in advance. B、The player makes up the music while playing. C、A good jazz player plays the same mu

Jazz began in the early 20th century as a music of African Americans. It was intended for singing, for dancing, for entertainment at parties and social gatherings.
    Jazz has continued to develop and has produced some of the United States leading singers, instrumentalists, and composers. Today, it is considered by many to be American’s art music. It has already influenced almost every other kind of music in America, Europe, and even Asia.
    The origin of the word "jazz" is not known, but the term came into common use after the first photograph records of Jazz were made in 1917. Jazz represents a mixture of musical elements from Africa and from Europe. Jazz uses some European ideas of harmony and melody, but the rhythms are more African in origin. It is usually said to be irregular in rhythm. And jazz uses many rhythms around one basic rhythm. Another important feature of jazz is that players can invent music while they are playing. This is the way jazz is usually played. Jazz musicians can make up excellent melodies as they play. A good jazz player seldom plays anything the same way twice. Thus, listening to jazz is not like hearing a piece of music that was written long ago. It is like being there when the music is first being made.
Questions 19 to 21 are based on the passage you have just heard.
19. What is Jazz considered now by many Americans?
20. How does Jazz include the elements from Africa and Europe?
21. What do you know about Jazz according to the passage?