Answer:
the hormone called Antidiuretic Hormone (ADH) is present
Explanation:
The collecting duct becomes more permeable to water when the hormone called Antidiuretic Hormone (ADH) is present.
It's a hormone present in the brain and produced by the pituitary gland. It controls amount of water in kidney. It also regulates and balances the amount of water in the blood.
This harmone is also known as called arginine vasopressin (AVP).
