Americans have contributed to many art forms, but jazz, a type music, is one of the art form that was started in the United States. Black Americans, who sang and played the music of their homeland, created jazz.
Jazz is a mixture of the music of Africa, the work songs the slaves sang, and religious(宗教) music. Improvisation is an important part of jazz. This means that the musicians make the music up as they go along, or create the music on the spot. This is why a jazz song might sound a little different each time it is played.
Jazz bands formed in the late 1800s. They played in bars and clubs in many towns and cities of the South, especially New Orleans. New Orleans is an international seaport, and people from all over the world come to New Orleans to hear jazz.
Jazz became more and more popular. By the 1920s, jazz was popular all over the United States. By the 1940s, you could hear jazz not only in clubs and bars, but in concert halls as well. Today, people from all over the world play jazz. Jazz musicians from the United　States, Asia, Africa, South America, and Europe meet and share their music at festivals on every continent. In this way jazz continues to grow and change.
What can be the best title of the passage?

A．American art forms.	B．The development of jazz.
C．The music of black Americans.	D．The birthplace of jazz.

Which of the following is true?

A．Jazz is now popular all over the world.

B．Jazz is now a kind of religious music.

C．Jazz is now played only in bars and clubs.

D．Jazz is now played a little differently sometimes.

From the text it can be inferred that_________ .

A．New Orleans is the place where jazz was first produced

B．the American people are all jazz lovers

C．jazz is merely sung by the black when working

D．jazz may become more popular as time goes on

It took about ________ years to make jazz popular in the United States.

A．200

B．120

C．80

D．140