The correct option is (a) Duck weed ponds
Explanation: Duck weed ponds grow profusely wherever there is nutrient rich waste water and they have higher nutrient harvesting efficiency and rapid growth properties, thereby organic and nutrient load in the waste water by syntrophic interactions and convert organic pollutants in fish biomass, Reed beds are a part of a succession from young reeds which colonize open water and can be used to treat liquid effluent, Water hyacinth pond is used for secondary and tertiary treatment, Algal fish ponds is used to increase the quality of water.