Black soil, also known as regur soil or black cotton soil, is one of the most fertile types of soil found in India. It is characterized by its dark color, high clay content, and excellent water-retaining capacity. Black soil is particularly suitable for growing cotton, hence its name "black cotton soil." Among the given options, black soil is found in Gujarat.

Gujarat:
- Gujarat is a state located in western India.
- It is known for its diverse landscapes, ranging from coastal areas to grasslands and desert regions.
- The state is blessed with a variety of soils, including black soil.
- Black soil in Gujarat is mainly found in the regions of Saurashtra and Kachchh.
- The black soil in Gujarat is a result of the weathering of volcanic rocks and basaltic lava flows.
- It is rich in nutrients like calcium, magnesium, potassium, and iron, making it highly fertile.
- The high clay content in black soil allows it to retain moisture, making it ideal for agriculture.
- Black soil in Gujarat is used for cultivating crops like cotton, groundnut, wheat, millet, and pulses.
- The fertile black soil of Gujarat has contributed significantly to the state's agricultural productivity.

Other Options:
- Jammu and Kashmir: Black soil is not found in Jammu and Kashmir. The soil types in this region are predominantly mountainous and include brown soil, loamy soil, and sandy soil.
- Rajasthan: Black soil is not found in Rajasthan. The state is known for its arid and semi-arid regions, where sandy and sandy-loam soils are more prevalent.
- Jharkhand: While Jharkhand has a variety of soil types, including red and laterite soils, black soil is not commonly found in this state.

In conclusion, black soil is found in Gujarat, making it an important region for agricultural activities, especially for crops like cotton and groundnut.