Explanation:
Carbon-14 is normally used to date living organisms (all living things we know today contain mostly carbon). It can be used for samples up to about 60000 years old. Carbon-12 is the non-radioactive form that we encounter daily. Relative dating determines dates relative to each other, such as ordering of period or events.
Uranium 235 dating can determine date samples a million years old and up, so is more suited for rocks.
