Concept:The diagram shows the longitudinal section of a mammalian kidney.
The kidney is a vital organ of the urinary system.
Explanation:The main parts visible are the outer cortex and the inner medulla.
The renal pelvis collects urine and leads into the ureter.
The kidney filters blood to remove waste substances such as urea.
It also helps to regulate water and salt balance in the body.
The filtered waste fluid is converted into urine.
Urine then passes from the pelvis into the ureter for removal.
This overall process of removing metabolic waste is called excretion.
Respiration, reproduction, and locomotion are not functions of the kidney.
Therefore, the organ is adapted primarily for excretion.
Answer:A. Excretion
