The correct option is B Vasopressin
Vasopressin or antidiuretic hormone is a potent endogenous hormone which is responsible for regulating plasma osmolality and volume. It acts as a neurotransmitter in the brain to control circadian rhythm, thermoregulation, and adrenocorticotrophic hormone release (ACTH).
The most potent stimulus for vasopressin release is an increased plasma osmolality.