Not sure if this is multiple choice but this is what I say.
Wind, composition of the tombstone and the PH level f any moisture that may come in contact with the tombstone.
Hope this helps if I'm not too late :)
b. radioactivity
The process by which atomic nuclei spontaneously decay is called radioactive decay. Explanation : This is also known as nuclear decay on a general basis In this process of radioactivity the unstable atomic nucleus loses energy .
Answer:
the image is blurry I cant see anything :((
