Complex organic compounds in sewage are broken down by bacteria. what is the role of bacteria in this? . a. bacteria act as nitrogen fixers. b. bacteria act as decomposers. c. bacteria act as catalysts..

Bacteria can be nitrogen-fixers, decomposers or agents/ catalysts. However, in the case, when the complex organic compounds in sewage are broken down by bacteria, the role of bacteria here is "as decomposers. Bacteria on this case decompose highly complex organic compounds.

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