Answer: Natural Errors
Explanation: Mutagens can erase parts of DNA that then replicate, but is not a mistake made in copying DNA so that's not it. UV Radiation distorts DNA, but is not necessarily a mistake made in copying it. Natural Errors are mutations made by cells when they copy base pairs and ineffectively or for some other reason mutate/do not create the correct DNA, and the failure of cells to correct this is a mutation. This is also known as an error in DNA replication
