A. The endocrine system uses hormones for signaling, while the nervous system uses neurotransmitters.: The endocrine system releases chemical messengers (hormones) into the bloodstream that act on distant targets, while the nervous system transmits signals using neurons that release neurotransmitters at synapses for rapid, localized communication. B. The endocrine system uses electrical signals, while the nervous system uses chemical signals.: The endocrine system relies on chemical hormones rather than electrical impulses; electrical signals are a primary feature of neuronal (nervous) communication. C. The nervous system generates responses that take longer to occur compared to the endocrine system.: Nervous-system responses are typically rapid and short-lived because of fast electrical conduction and synaptic transmission, whereas endocrine responses are usually slower to start but longer-lasting. D. Both systems use hormones for signaling but at different speeds.: While the endocrine system primarily uses hormones, the nervous system mainly uses electrical impulses and neurotransmitters; hormones can modulate neural function but the two systems do not both primarily use hormones.