Answer:
mountains, deserts
Step-by-step explanation:
China is a large country with diverse geography. While the river valleys in China have some of the richest soil in the world, the majority of the land in China is mountainous or desert, making it difficult for agriculture.
The mountainous regions, such as the Himalayas, Kunlun Mountains, and Tian Shan, make up over two-thirds of China's land area. These areas are difficult to farm due to steep slopes, poor soil quality, and harsh climates.
The deserts, such as the Gobi Desert and the Taklamakan Desert, cover a significant portion of the country as well. These regions have extremely arid climates and limited water resources, making agriculture challenging.
Therefore, despite the rich soil in the river valleys, only a small portion of China's land can be farmed due to the predominance of mountains and deserts.