Which of the following adaptations helps maximize gas exchange in fish?

Gill filaments with lots of blood capillaries are a key adaptation that maximizes gas exchange in fish. The primary function of gills is to extract oxygen from water, and the structure of the gill filaments plays a crucial role in this process.

The filaments are thin and have a large surface area, which increases the rate at which gases can diffuse across the membranes. Additionally, the presence of many blood capillaries within the filaments ensures that oxygen can efficiently enter the blood and carbon dioxide can be expelled. This close association between the water flowing over the gills and the blood in the capillaries creates a concentration gradient, facilitating effective gas exchange.

This adaptation is essential for fish because they rely on water, rather than air, to obtain oxygen, making their gills an efficient mechanism for respiration in an aquatic environment. Other options, while they may contribute to the overall function of the fish, do not specifically enhance the efficiency of gas exchange as effectively as the specialized structure of gill filaments.