First of all, from the origin of time:
1. The earliest written record of guqin can be found in the Book of Songs, which proves that guqin has been popular at least in the Zhou Dynasty.
2. The earliest written record of guzheng should be regarded as a strategy in the Warring States policy. There are many sources, but at least it proves that it became popular during the Warring States Period.
3. Erhu began in Tang Dynasty and was recorded by Chen Yi, a scholar of Ning Dynasty, in Le Shu.
4. The flute has a recording source. Custom Tong records the origin of flute making in the period of Emperor Wu of Han Dynasty.
5. Historical investigation of suona furniture that spread in Persia (Iranian) and was introduced into China in Jin and Yuan Dynasties.
6. It is said that loquat originated in Qin Dynasty. The earliest record is Liu Xi's interpretation of musical instruments in Han Dynasty.
To sum up, from the origin of time, guqin can best represent Chinese musical instruments.
Second, in terms of regional culture:
1, Huaxia nationality refers to the earliest group of residents in the Yellow River and Yangtze River basins. That is, according to what we are saying now, it is mainly Han nationality. Guqin originated in this area.
Erhu, flute, pipa, suona and so on are all Chinese musical instruments. But most of the origins come from ethnic minorities.
Therefore, Guqin is the most representative national musical instrument in China.
I searched the information according to the subject's question and came to the above two conclusions. If you have different opinions, you can discuss them with each other.