Every living thing needs ? to survive. (water, oxygen, carbon dioxide)

When children are young and go to the doctor, the doctor will give them booster shots. this re-exposes the children to a dead portion of a disease to them build immunity.

What is the main difference between trace elements and the main elements that make up the body? 1) main elements consist of heavier atoms. 2) trace elements are only needed in small amounts. 3) trace elements consist of heavier atoms. 4) main elements are only needed in small amounts.

Most of the phosphorus on earth comes from ?