Answer:
cleaning
Explanation:
If people would clean up after themselves, the world's rivers and lakes would be clean. Water pollutants can be somewhat easy to remove by taking the trash out of them.
Number 1: The Circulatory System is a vast network that contains organs and vessels.
number 2: Arteries have a thick wall which helps a powerful pressure from the heart.
number 3: Without the Circulatory System the body wouldn't be unable to maintain a internal environment.
number 4: The Circulatory and Respiratory system both have gas to help a or animal live in there internal environment.
number 5: Blood vessels brings oxygen to the tissues and absorbs carbon dioxide and other waste products to clear the lungs. And with out oxygen the tissues won't absorb carbon dioxide to clear out the lungs.
number 6: D
Answer:
combustible ....................
Im not 100% sure but the best answer I can give is Prokaryotes because they came to be around the time oxygen did as well.
