Valves ensure blood flows toward your heart. Vein valves work to bring the blood that flowed down via arteries back up to your heart.
Answer: D
Explanation:
Because the heavy plow and its traction team was expensive tool and individual peasant farmers were not able to own it, it brought collective ownership and patterns of communal agriculture and communal animal husbandry.
The heavy plough required more energy to pull this resulted several families coming together to pool their oxen to form a team large and strong enough to pull the heavy plow. The resulting “ox-gangs” became an important social group.
They are used to directly amplify segments of dna
Because the life is adapted to that biome.
