Which one of the following statements is correct?

Rhizobium fix nitrogen in root nodules of legumes, while Azotobacter is a free-living nitrogen-fixing bacterium. Anabaena and Nostoc are not mobilisers of phosphates. Anabaena is a filamentous cyanobacteria, involved in nitrogen fixation. Extensive use of chemical fertilizers may lead to eutrophication of nearby waterbodies. Related Theory Eutrophication or more precisely hypertrophication, refers to enrichment of $a$ water body with nutrients, usually with an excess amount of nutrients. This process induces growth of plants and algae and, due to the biomass load, may result in oxygen depletion of the water body. For example, algal bloom.