The correct option is D Hormone
Glands are divided into two categories - exocrine and endocrine glands.
Exocrine glands release their products through ducts. These glands secrete mucus, saliva, earwax, oil, milk, digestive enzymes, etc. Exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous.
Endocrine glands do not have ducts. So, they are called ductless glands. Their products (hormones) are secreted directly into the fluid. Some examples of endocrine glands are the pituitary, thyroid, and adrenal glands.