Answer:
During a chemical change, the composition of matter always changes. Four possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate.
Explanation:
Organisms that use the same resources because there may not be enough for all, so it then becomes a competition of who gets it and who doesn't.
Valves, they are like flaps of muscle that keeps the blood in its place util its ready to be pumped along.
