The correct answer is: Alluvial.
Alluvial soil is a type of soil that is formed from the deposition of sediment by water. It is the most common type of soil in Haryana, and it is also found in other parts of India, such as the Ganges Plain. Alluvial soil is very fertile, and it is used for a variety of crops, including rice, wheat, and sugarcane.
Black cotton soil is a type of soil that is found in the Deccan Plateau of India. It is a rich, dark soil that is well-suited for growing cotton. However, it can be difficult to work with, as it is sticky and heavy.
Red laterite soil is a type of soil that is found in tropical and subtropical regions. It is a reddish-brown soil that is low in nutrients. It is not well-suited for agriculture, but it is used for building materials.
Desert sand is a type of soil that is found in deserts. It is a loose, sandy soil that is low in nutrients. It is not well-suited for agriculture, but it is used for building materials.
In conclusion, the correct answer to the question “Soil types in Haryana’s plains are mostly: Alluvial / Black cotton / Red laterite / Desert sand” is Alluvial.