Answer:
C, carbon dioxide and water
Compared to arteries, valves have no pulse, have thin walls and have valves that prevent backflow of the blood. The pressure in the veins is less than that of the arteries, hence, there is no pulse. They are nearer to the surface of the skin. It also connects arteries and capillaries which transport blood all throughout the circulatory system.
Humans evolved 3 billion years ago after the earth was formed.<span />
Autotroph is to producer as Hetrotroph is to consumer
Autotrophs make their own food, which makes them producers
While Hetrotrophs cannot make their own food, and must obtain it from another source, making them consumers
Earth science hope it helps
