<span>Sterilization of animals reduces the level of circulating reproductive hormones leading to increased longevity, typically due to reduce cancer mortality. The primary aim of animal sterilization is avoiding overpopulation, but this increased longevity could be an added benefit for an individual animal.</span>
The sunlight provides energy for the plants to grow. <span>Since it is a closed system, no water would be lost, so it is not necessary to add extra water. </span>
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 :)