Americans have contributed (做贡献) to many art forms, and jazz, a type of music, is one of the art forms 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 (即兴表演) is an important part of jazz. This is why a jazz song sounds 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

From the text we can learn that ______.

A．New Orleans is the place where jazz was very popular

B．the American people are all jazz lovers

C．jazz is merrily sung by black people when working

D．jazz may become less popular as time goes on

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

A．200

B．120

C．80

D．40