Lucky People Who Cannot Be Infected with HIV Are Protected

question 39

Multiple Choice

Lucky people who cannot be infected with HIV are protected because

• A) they are already infected.
• B) their cells lack receptors that admit the virus.
• C) their cells have extra receptors for HIV.
• D) they were vaccinated.

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Definitions:

Friction

The resistance that one surface or object encounters when moving over another.

Scales

Small, rigid plates that grow out of an animal's skin to provide protection. In fish and reptiles, scales perform this protective function.

Adaptation

The process by which organisms adjust to changes in their environment in order to survive and reproduce.

Creep

The slow movement of soil or rock down a slope, driven by gravity.