Consists of glands that control many of the body's activities by producing hormones.

• A. Nervous system
• B. Digestive system
• C. Muscular system
• D. Endocrine system

Answer: (D)

Hormones regulate many body activities by being released from glands into the bloodstream and traveling to distant targets. The endocrine system is made up of glands such as the pituitary, thyroid, adrenal, pancreas, and gonads, which secrete hormones that control metabolism, growth, reproduction, and responses to stress. This differs from the nervous system, which uses rapid nerve signals, and from the muscular system, which enables movement; the digestive system involves glands for digestion but is not defined by circulating hormones that regulate multiple body activities. So the described system is the endocrine system.