Compounds that exist naturally in plants and a plant proect itself from bacteria and disease are called

Explanation:In the root nodules of many legumes, symbiotic nitrogen-fixing bacteria called Rhizobia reside. The relationship between a host legume and the Rhizobia is symbiotic or mutualistic in which both partners get benefit.  Once the Rhizobia have established themselves in the root nodule, the plant provides carbohydrates (food) to the bacteria, and in return the Rhizobia provide ammonia for the formation of amino acids and nucleotides.  

b is the best answer for this question.

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