We can control it. It's just that our world "leaders" seem to use use money and drugs for other things. It cost money to even make money, yet, people don't want to spend it.
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 :)
Answer:
cells
Hope This Helps! Have A Nice Day!!
This would be an example of D. <u>Founder Effect</u>