Rice is the predominant crop grown in Arunachal Pradesh, primarily in:

The correct answer is: b) Valley and foothills.

Rice is a tropical crop that requires a lot of water. The high altitude regions of Arunachal Pradesh are too cold and dry for rice to grow. The dryland areas of Arunachal Pradesh also do not have enough water for rice to grow. The semi-arid regions of Arunachal Pradesh have some water, but not enough for rice to grow well. The valley and foothills of Arunachal Pradesh have the right combination of temperature, rainfall, and soil for rice to grow well.

Here is a brief explanation of each option:

• High altitude regions: These regions are too cold and dry for rice to grow. The average temperature in these regions is below 10 degrees Celsius, and the annual rainfall is less than 1,000 millimeters.
• Dryland areas: These areas do not have enough water for rice to grow. The average rainfall in these areas is less than 500 millimeters, and the soil is not very fertile.
• Semi-arid regions: These regions have some water, but not enough for rice to grow well. The average rainfall in these regions is between 500 and 1,000 millimeters, and the soil is not very fertile.
• Valley and foothills: These areas have the right combination of temperature, rainfall, and soil for rice to grow well. The average temperature in these areas is between 10 and 20 degrees Celsius, the annual rainfall is between 1,000 and 2,000 millimeters, and the soil is fertile.