GED Science Practice 2025 - Free GED Science Practice Questions and Study Guide

Natural immunity refers to the type of immunity that an individual is born with, which is part of their inherent biological makeup. This form of immunity provides immediate defense against infections and diseases without the need for prior exposure to the pathogen. This can involve physical barriers like skin and mucous membranes, as well as innate immune responses that include various cells and proteins that act quickly when pathogens invade.

While factors like the nucleus, natural selection, and nearsightedness pertain to biological or environmental concepts, they do not directly relate to the body's defense mechanisms against diseases. The nucleus is a cell structure that contains genetic material, natural selection refers to the process by which organisms better adapted to their environment tend to survive and reproduce, and nearsightedness is a vision condition unrelated to disease immunity. Therefore, the correct identification of natural immunity highlights its vital role in providing innate protection from various diseases as part of the body's fundamental defense system.