Final answer:
The water output is largely controlled by varying urine volume. The kidneys regulate water levels in the body, conserving water when needed and expelling excess water. ADH hormone aids in water retention.
Step-by-step explanation:
The water output is largely controlled by the varying urine volume. The kidneys play a crucial role in regulating water levels in the body. They can conserve water if the body is dehydrated or make urine more dilute to expel excess water when necessary. ADH, a hormone, helps the body retain water by increasing water reabsorption by the kidneys.