The main crop of Assam is

The main crop of Assam is rice. It is grown in the Brahmaputra valley and the Barak valley. The state is the largest producer of rice in India. Rice is a staple food in Assam and is used to make a variety of dishes, such as aloo bhaja, bhaat, and pitha.

Wheat is not a major crop in Assam. It is grown in some parts of the state, but it is not as important as rice. Wheat is used to make a variety of dishes, such as roti, chapati, and paratha.

Mesta is a type of cotton that is grown in Assam. It is not as important as rice or wheat. Mesta is used to make a variety of clothes, such as dhotis, saris, and kurtas.

Therefore, the correct answer is A.