Physical barriers that help prevent an individual from contracting diseases include __________.

• A. antibodies in the bloodstream
• B. phagocytic white blood cells
• C. complement proteins
• D. intact skin and mucous membranes

Answer: (D)

Verified step by step guidance

1. Understand that physical barriers are the body's first line of defense against pathogens, preventing their entry into the body.
2. Identify examples of physical barriers, which include intact skin and mucous membranes that act as protective layers.
3. Recognize that antibodies in the bloodstream, phagocytic white blood cells, and complement proteins are part of the immune system but are not physical barriers; they function after pathogens have entered the body.
4. Focus on the role of intact skin as a tough, impermeable barrier that blocks pathogens from entering the body through external surfaces.
5. Understand that mucous membranes line body cavities and secrete mucus, which traps microbes and prevents them from invading deeper tissues.