The ability of body to defend itself against scientific invading agent such as bacteria, toxin, viruses, and foreign body:

Correct Answer: C. Immunity

Immunity is the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells. The Immune response is the body’s ability to stay safe by affording protection against harmful agents and involves lines of defense against most microbes as well as specialized and highly specific responses to a particular offender. This immune response classifies as either innate which is non-specific and adaptive acquired which is highly specific.

• Option A: The endocrine hormones are a wide array of molecules that traverse the bloodstream to act on distant tissues, leading to alterations in metabolic functions within the body. They can broadly divide into peptides, steroids, and tyrosine derivatives that may work on either cell surface or intracellular receptors.
• Option B: Secretion, in biology, production and release of a useful substance by a gland or cell; also, the substance produced. In addition to the enzymes and hormones that facilitate and regulate complex biochemical processes, body tissues also secrete a variety of substances that provide lubrication and moisture.
• Option D: A gland is an organ which produces and releases substances that perform a specific function in the body. There are two types of gland. Endocrine glands are ductless glands and release the substances that they make (hormones) directly into the bloodstream.