The answer is A because they need the sunlight to go through the water
Answer:
Option D, It is highly efficient, as oxygen-rich air enters the lungs even while a bird is exhaling
Explanation:
In the respiratory system of birds, air flows only in one direction due to which a bird is capable to take in oxygen even when it is exhaling. The air sacs allow only unidirectional flow of air, which is more fresh and contains high oxygen content. Even a bird’s lung are capable to store and pump air, when they are at stationary position.
Hence, option D is correct.
Think of it like this. Horses do a LOT of galloping, which is hard on the feet! Hooves are a physical ADAPTATION, so that the horses won't experience pain on their journeys. They're hard, so that the horses don't feel the ground nearly as much. Now, mountain goats travel over rough terrain, with sharp rocks and steep inclines. Again, it's really easy for them to get hurt strutting around the mountains, so they evolved hard hooves to protect their feet.
<span>A joint united by dense fibrocartilaginous tissue that usually permits a slight degree of movement is a symphysis.</span>