The one without a nucleus.
Both protons and neutrons have the highest atomic mass
They clean the animals because, the oil will harm them otherwise. Meaning if the oil stay s on them long enough, it can harm them dramatically; In ways in which it may cause death.
Since chemical spills are very harmful to aquatic/land life for both plants and animals, plants probably wouldn't grow back and animals could be mutated or even killed, decreasing the population of that species. A volcano eruption, can be both good and bad, since a volcano can kill animals and plants, but ash from a volcano is extremely fertile, so plants can regrow, which in turn brings animals back so they can feed on those plants.
