The correct answer is C. Endocrine gland.
An endocrine gland is a ductless gland that secretes hormones directly into the bloodstream rather than through a duct. The hormones produced by endocrine glands regulate many important body functions, such as growth, metabolism, and reproduction.
The liver is an organ that performs many important functions in the body, including detoxification, metabolism, and blood clotting. It is not an endocrine gland.
Sweat glands are exocrine glands that produce sweat, which helps to cool the body. They are not endocrine glands.
The kidneys are organs that filter waste products from the blood and produce urine. They are not endocrine glands.