Which of the following assists with gas exchange in human lungs?

The option highlighting a moist lining is correct because the moist environment in the lungs is essential for effective gas exchange. Alveoli, the tiny air sacs in the lungs where gas exchange occurs, are lined with a thin layer of moisture. This moisture helps to dissolve oxygen and carbon dioxide, making it easier for these gases to diffuse across the alveolar membrane into and out of the bloodstream. The thin moisture layer minimizes the distance that gases need to travel, enhancing the efficiency of the exchange process.

In contrast, thick walls would hinder gas exchange, as they create a greater distance for diffusion. A low surface area would also be detrimental, as it reduces the area available for gas exchange, limiting the amount of oxygen that can be absorbed and carbon dioxide that can be expelled. Finally, a poor blood supply would impair the transport of gases to and from the alveoli, making gas exchange less effective. The moist lining thus plays a pivotal role in facilitating optimal gas exchange within the lungs.