Which of the following is true about aquatic vertebrates?

Aquatic vertebrates indeed have many adaptations for swimming, which is why this choice is correct. These adaptations can include streamlined bodies, fins, and specialized musculature that allow for efficient movement through water. Such features are crucial for their survival in aquatic environments, as they enable them to navigate, hunt for food, evade predators, and maintain their position within the water column.

In contrast to this, not all aquatic vertebrates lay eggs on land, as many, like fish and amphibians, lay their eggs in the water. Also, while some aquatic vertebrates, like certain amphibians, may possess lungs, many aquatic organisms, such as fish, primarily use gills for respiration under the water. Lastly, aquatic vertebrates are not solely found in freshwater; they inhabit a range of environments, including saltwater oceans, brackish waters, and various freshwater habitats. This diversity further emphasizes the importance of specific adaptations for swimming, as these adaptations vary widely among different species depending on their habitat.