You are presented with the question "what is used to determine the age of fossils?" and the following answer choices: 
- Conifers
 - Sediment
 - calcite
 - skull
 - loose soil
 - cracking
 - exoskeleton
 - isotopes

Now knowing that radioactive dating is used to determine the age of fossils and radioactive isotopes are commonly used for dating , choose the best answer.


 

        isotopes 