Answer:
C
Explanation:
C is the answer ur looking for ;)
Everything has mass. The mass of something never changes.
Mass is measured using grams.
Air is not that heavy, but it certainly has mass because it takes up space.
For every one liter of air, their is 1.19 grams.
Valves ensure blood flows toward your heart. Vein valves work to bring the blood that flowed down via arteries back up to your heart.
C is the proper answer. They have been reduced by using unleaded gasoline because lead can harm the air and water we breathe, so using less of it will help reduce the pollution being caused by it.
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.
