Answer:
1. Excretion
Step-by-step explanation:
Excretion is the process of removal of metabolic waste from body. Excretory system of human being includes kidneys as the primary organ of urine formation and removes the urea from the body. Since urea was once a metabolite in the body, it is called as metabolic waste. Breakdown of amino acids in liver produces ammonia as by production which in turn is converted into urea in liver itself.