Within the body; pertaining to the inside of the body, opposite of external?

• A. External
• B. Peripheral
• C. Central
• D. Internal

Answer: (D)

The main idea here is choosing a term that directly means “inside the body.” Internal is the word that describes something located within the body's boundaries, inside its structures or cavities. It contrasts with external, which denotes things on or outside the body’s surface. So when we say something is inside, inside the body, or within a body cavity, internal is the appropriate descriptor.

Think of internal organs like the heart or lungs as examples of internal features, in contrast to the outside surface like the skin. Central and peripheral describe position relative to a center or edge, not specifically inside versus outside, so they don’t fit as the opposite of external in this context.