Microbes enter the human body most frequently through the ______ and ______ mucosa.

• A. ocular; auditory
• B. urinary; reproductive
• C. cutaneous; synovial
• D. respiratory; gastrointestinal

Answer: (D)

Verified step by step guidance

1. Identify the common entry points for microbes into the human body by considering the mucosal surfaces that are most exposed to the external environment.
2. Recall that mucosa refers to the moist linings of body cavities that are exposed to the outside, such as the respiratory tract, gastrointestinal tract, urinary tract, and reproductive tract.
3. Understand that the respiratory mucosa (lining the nose, throat, and lungs) is a primary entry point because it is constantly exposed to air and airborne microbes.
4. Recognize that the gastrointestinal mucosa (lining the mouth, stomach, intestines) is another major entry point due to ingestion of food and liquids that may contain microbes.
5. Conclude that the respiratory and gastrointestinal mucosa are the most frequent routes for microbial entry, rather than ocular, auditory, urinary, reproductive, cutaneous, or synovial surfaces.