b. It allows gas exchange while preventing water loss
Explanation:
Amniotic eggs are the feature of land animals such as reptiles, birds, mammals, etc. The amniotic eggs have four extra-embryonic membranes. This semipermeable protective shell allows the exchange of respiratory gases but does not support the transport of water out of the egg.
The ability to maintain the water inside the egg while permitting gaseous exchange is the specific feature of amniotic eggs and allowed diversification of land animals in the land habitats.
Arteries carry oxygenated blood away from the heart. Veins carry the blood back to the heart. Veins contain valves that ensure blood flows in only one direction. Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.
