Answer:
This statement is true, as the inner core is the most dense layer of the earth.
Answer:
Muscles pull on the joints, allowing us to move.Muscles make up half of a person's body weight. They are connected to bones by tough, cord-like tissues called tendons, which allow the muscles to pull on bones. If you wiggle your fingers, you can see the tendons on the back of your hand move as they do their work.
The right answer is vein (it contains blood and has valves).
The infra-cardiac veins of small and medium caliber possess this system of fight against gravity. The valves consist of a dense connective tissue, surmounted by endothelial cells, corresponding to a fold of the intima. They allow blood circulation in the sense organ / heart but prevent venous reflux.
I believe the answer is (B)
<span>a complex series of feeding relationships with many organisms interacting and depending on each other </span>
