A hormone acts on a specific tissue or organ that has receptors for it. This defines the hormone’s:

• A. Systemic reach
• B. Target organ
• C. Mode of transport
• D. Metabolic rate

Answer: (C)

The key idea is receptor specificity. A hormone elicits effects only in tissues that have receptors for it, so the tissue that contains those receptors is the target organ. The way the hormone travels to that tissue (for example, through the bloodstream in endocrine signaling) is its mode of transport, not what tissue will respond. So the defining concept here is the target organ. Concepts like systemic reach or metabolic rate relate to distribution or metabolism, not to which tissue can respond to the hormone.