<span>The thing that might happen to the tree was it might get swept away by the current until it catches on something or disappears (dissolves). The tree will going to the flow of the river until it catches on something where it may disappears or dissolve.</span>
Valves ensure blood flows toward your heart. Vein valves work to bring the blood that flowed down via arteries back up to your heart.
Supply oxygen to cells for cellular respiration.
Answer:
B.secrete hormones directly into the bloodstream
