1 Assimilating some parts of substances that is no longer required by the body.
2 Removal of nitrogenous wastes from the body
3 Removal of useful substances from the body
4 Removal of undigested food formed during digestion
Explanation:
Excretion refers to the process of removal of nitrogenous wastes from the body of living organisms, which get accumulated due to the various metabolic activities and by other means such as excess ingestion.