PLEASE HELP ME! Biology question??? easy 10 pionts.?

Carbon is the molecule of choice because it can be used for all living things, because all animals have to breathe, producing carbon, so we will constantly have a new supply of carbon in our bodies, until the day we die. So it is very accurate at measuring the exact time when something died, but it is hard/impossible to tell when something was born/how old it was. It is also used because it has a relatively long half life.