The pulmonary circuit:

Innate defenses counter specific disease-causing agents, whereas adaptive defenses include mechanical and chemical barriers.

Choice A is wrong because it confuses the two types of defenses.

Innate defenses are nonspecific and include physical barriers such as the skin, molecules that are toxic to invaders, and phagocytic cells that ingest invaders.

Adaptive defenses are specific and are activated by the innate immune system.

They involve the production of antibodies and specialized cells that recognize and eliminate specific pathogens.

Normal ranges are not applicable in this question as it is about the definitions of innate and adaptive defenses.

Paracrine secretions are chemical signals that affect only nearby cells.

They are released by the sending cell and diffuse through the extracellular space to the target cell, which has a specific receptor for the signal.
Paracrine signaling is a form of local signaling that occurs in multicellular organisms.
Choice A is wrong because autocrine secretions are chemical signals that act on the same cell that produced them.
Autocrine signaling is also a form of local signaling, but it involves cell signaling itself.
Choice B is wrong because endocrine secretions are chemical signals that are secreted into the blood and act at long distances.
Endocrine signaling is a form of long-range signaling that involves ductless glands that secrete hormones.
Choice C is wrong because exocrine secretions are non-hormonal substances that are secreted into ducts to the external environment.
Exocrine signaling is not a form of cell-cell communication, but rather a way of releasing substances such as sweat, saliva, or digestive enzymes.