题目内容：

The guzheng is a traditional Chinese musical instrument. It belongs to the zither（齐特琴）family of string instruments. It is the parent of many musical instruments of some other countries.

The guzheng should not be confused with the guqin, another ancient Chinese zither but without bridges. Now the guzheng is zither with movable bridges and usually 21 strings, although it can have from 15-25 strings. The guzheng’s strings were formerly made of silk, though most players used metal strings by the 20th century. Since the mid-20th century most performers use steel strings. The guzheng has a large resonant cavity（共振腔）.

The guzheng has existed since the Warring States Period and became especially popular during the Qin dynasty. The number of strings on the guzheng has always fluctuated. There were as few as 6 to as many as 23 strings during the Tang dynasty. The earliest record of the guzheng belonged to the historian Sima Qian. Until 1961, the common guzheng had 16 strings, although by the mid-20th century 18-string guzheng were also in use. In 1961, Xu Zhenggao, together with Wang Xunzhi, introduced the first 21-string guzheng after two years of research and development. In 1960, they also invented the “S-shaped” left string rest, which was quickly adopted by all guzheng makers and is still used today. This curve allows for greater ease in tuning the strings and, combined with strings of different thickness, allows for greater resonance in both the deeper and the higher pitch（音调）ranges. The 21-string guzheng is the most commonly used one, but some traditional musicians still use the 16-string one.

1.We can infer from Paragraph 1 that ________.

A. the guzheng is a musical instrument originating from Japan

B. there is only one kind of string instrument in China

C. there are many kinds of guzheng in the world

D. many musical instruments in other countries are related to the guzheng

2.Which of the following material may NOT have been used to make the strings of the guzheng probably?

A. Silk    B. Steel

C. Wood    D. Copper

3.The underlined word “fluctuated” in paragraph 3 can be replaced by “________”.

A. jumped    B. changed

C. flowed    D. waved

4.Which of the following statements is true according to the passage?

A. The guqing is an ancient Chinese zither with bridges.

B. The guzheng became espevially popular in the Tang Dynasty

C. All musicians don’t use the 21-string guzheng.

D. Xu Zhenggao invented the “S-shaped” left string rest himself.