Which of the following are nitrogen-fixing plants ? 1. Alfalfa 2. Amaranth 3. Chickpea 4. Clover 5. Purslane (Kulfa) 6. Spinach Select the correct answer using the code given below :

Option (a) is correct because Alfalfa, Chickpea, and Clover are leguminous plants that perform biological nitrogen fixation through symbiotic relationships with *Rhizobium* bacteria in their root nodules. Amaranth, Purslane, and Spinach are non-leguminous plants that do not fix nitrogen, making options (b), (c), and (d) incorrect as they include these species. The core concept being tested is the identification of nitrogen-fixing species, which are primarily members of the Fabaceae (legume) family.