Concept:Legumes are unique due to their root nodules that host nitrogen-fixing bacteria.
Explanation:Legumes form a symbiotic relationship with
Rhizobium bacteria in nodules on their roots.
These bacteria convert atmospheric nitrogen into nitrogenous compounds, enriching the soil and the plant.
Grasses do not form such root-nodule associations.
This feature is a key distinguishing characteristic of legumes.
Answer:B. They form symbiotic relationship with bacteria, rhizobium, in the nodules of their roots.