Final answer:
Mucous membranes line body cavities that open to the external environment, such as the respiratory, digestive, urinary, and reproductive tracts. They provide a barrier to pathogens and keep internal surfaces moist with secretions like mucus. The correct answer to the question is 'd. mucosa.'
Step-by-step explanation:
The mucous membranes line body cavities that open to the external environment. They are found lining the respiratory, digestive, urinary, and reproductive tracts. These membranes feature a combination of epithelial tissue and an underlying connective tissue layer known as the lamina propria. They are essential for protecting the body by trapping pathogens and removing them through secretions such as mucus.
The correct answer to the question of which of the following lines the body cavities exposed to the external environment is d. mucosa. This is because mucosa, or mucous membranes, cover the inside layer of the body's hollow organs and structures that are exposed to the outside environment. Not only do they provide a mechanical barrier to pathogens, but they also keep epithelial surfaces moist and contribute to immune defense.