Which system includes glands like thyroid and adrenal?

• A. Cardiovascular
• B. Nervous
• C. Endocrine
• D. Digestive

Answer: (C)

The endocrine system uses hormones released by glands into the bloodstream to regulate metabolism, growth, and stress responses. Thyroid and adrenal glands are classic endocrine glands because they secrete hormones directly into the blood to reach distant targets. This hormonal signaling distinguishes them from the cardiovascular system (which moves blood), the nervous system (which uses rapid electrical signaling), and the digestive system (which handles breakdown and absorption of nutrients).