The Yellow Mountain is one of the most famous m____  in China. Every year l____  of Chinese people and foreigners visit it. It is not f____  from here. You can s____ about two hours getting there by bus. You can also go there by train o____  by plane. When you are c____ the mountains, you can e____  the sea of clouds, wonderful trees and rocks (岩石) a____ you. In the e____ morning when the sun rises (升起)，the sun looks b____ . It is really a good place to go.

郭沫若说“由秦到现在两千多年了，我们依然感觉着春秋战国在学术思想史上是中国的黄金时代。”是因为春秋战国出现（    ）