The first test is the heart
Answer: The things that are listed .
Explanation: The circulatory system is made up of blood vessels that carry blood away from and towards the heart : Arteries carry blood away from the heart and veins carry blood back to the heart .
Answer:
The blood picks up co2 and also waste from the tissue. So I am guessing that it is co2.
Hope this helps.
Yes, there is a variety of things you can do to wear down the enamel. A few of the biggest things are: Drinking Coffee or soda, eating acidic foods and not brushing your teeth. Sadly you are not able to grow back your enamel after if it fully gone so it's best to protect your enamel as much as possible.