Answer:
d. decomposition
Explanation:
If an organism is living and feeding on dead and decaying matter like dead leafs and food scraps then the process is known as decomposition and the organism is known as decomposer.
In decomposition, complex bio-molecules like proteins are broken down into simpler ones and then nutrients like nitrogen, phosphorus etc are recycled back into the environment so that they could be reused by plants to make complex bio-molecules once again. Bacteria use their digestive enzymes to decompose such dead and decaying matter and as a result of decomposition they obtain energy for their day to day activities.
Apart from bacteria, fungi also perform decomposition.
