The correct option is C Mustard
Mixed Cropping is growing of two or more crops simultaneously on the same piece of land. This type of cropping leads to an improvement in the fertility of the soil and
hence increase in crop yield because when the two crops are properly chosen, the products and refuse from one crop help in the growth of the other crop plant and vice-versa.
For E.g Wheat requires nitrogen for its growth and mustard is a leguminous plant which fixes nitrogen in he soil.