The correct answer is: B. alluvial soil
Alluvial soil is the most common type of soil in Bihar. It is a type of soil that is formed by the deposition of sediments from rivers and streams. Alluvial soil is typically rich in nutrients and is well-drained, making it ideal for agriculture.
Mountainous soil is a type of soil that is found in mountainous regions. It is typically thin and rocky, and it is not well-suited for agriculture.
Regur soil is a type of soil that is found in semi-arid regions. It is typically rich in iron and aluminum oxides, and it is not well-suited for agriculture.
Terai soil is a type of soil that is found in the Terai region of Nepal and India. It is typically a mixture of alluvial soil and loamy soil, and it is well-suited for agriculture.
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