阅读下面的短文，从每题所给的四个选项(A、B、C、D)中，选出最佳选项。
E
Some dances gain more popularity than others because they can be performed to different kinds of music and the steps change accordingly. One such dance is the waltz.

There is a basic form for the waltz, which you can see in this drawing of a dancing couple. The man places one arm around the woman's waist and she places her opposite hand on his shoulder. Then, they stretch their arms out from their bodies and clasp hands. If someone tries to teach you a formal kind of dancing, chances are you teacher will start with the waltz. Have you ever tried to dance like this?
There are lots of different kinds of waltzes, all performed to different types of waltz music. The music might be fast or slow but what they all have is a regular onetwothree, onetwothree rhythm.
The traditional form is the oldschool waltz in which dancers turn all the time with a hopping, springy step. This waltz has a slow, smooth, gliding step. There's also the Mexican watlz, which moves much faster. Listen to this Mexican watlz music and you can imagine how fast the dancers had to move.
Formal dancing has even become a profession, with people entering competitions. Have you ever seen a formal dance competition?
Today, ballroom dancing is almost considered a competitive sport; professionals perform different dancers, each with strict rules. Everything from where the dancers place their hands to how they move is judged. In the glide waltz, dancers are judged by how smoothly they move. “I can dance with a glass of water on my head，”is a well known sentence used by skilled dancers in the old days. In the past, some people learned how to dance by reading books, while others studied with a teacher called the“dancing master.” How do people learn to dance today?
When a couple are dancing, ________.

A．the girl places one arm around the man's waist

B．the man puts one hand on the girl's shoulder

C．they stand face to face with one of their hands held together

D．the man puts one arm around the girl's waist and the other on her shoulder

Why do the dancers move fast in the Mexican waltz?

A．To keep up with the music.

B．To show how well they perform.

C．To catch up with the other dancers.

D．To show the difference of the dance.

What do the different types of Waltz have in common?

A．They use the same kind of music.

B．They share the same kind of steps.

C．Their speed are the same.

D．They have the same kind of rhythm.

If one says“I can dance with a glass of water on my head”， we know that________.

A．he is a good dancer

B．he is a beginner

C．he is practicing dancing

D．he is tired of dancing