Carbon dating decay equation
The amount still present in a sample of what was once a living creature can thus be used to determine its age.
Carbon 14 can also be used as a radioactive marker.
Obviously this only works for things which once contained carbon—it can’t be used to date rocks and minerals, for example. We obviously need to know this to be able to work out at what point the ‘clock’ began to tick.
The fact that the N doesn’t matter in a living thing—because it is constantly exchanging carbon with its surroundings, the ‘mixture’ will be the same as in the atmosphere and in all living things.
Finally, CO2 molecules with radiocarbon, absorbed by vegetation, enter natural environment (D).