Option 1: Wheat -

Wheat is a cereal crop and does not have the ability to fix nitrogen from the air. It requires a sufficient amount of nitrogen to grow but does not contribute to enriching the soil with nitrogen.

Option 2: Mustard -

Mustard is a green manure crop that is known for its ability to fix atmospheric nitrogen through a symbiotic relationship with soil bacteria. When mustard plants are plowed back into the soil, they release nitrogen, which can enrich the soil and benefit the subsequent crop. Therefore, mustard is a good choice for enriching the soil with nitrogen.

Option 3: Sunflower -

Sunflower is not a nitrogen-fixing crop. It does not have the ability to convert atmospheric nitrogen into a form that can be used by plants. Planting sunflower may not contribute significantly to enriching the soil with nitrogen.

Option 4: Gram -

Gram, also known as chickpea, is a leguminous crop that is known for its ability to fix atmospheric nitrogen through a symbiotic relationship with soil bacteria. When gram plants are plowed back into the soil, they release nitrogen, which can enrich the soil and benefit the subsequent crop. Therefore, gram is a good choice for enriching the soil