Answer:
These are things that won't be going away. Natural gasses and fossil fuels will likely run out someday or become much harder to find. When you use these sources of energy, they won't be going away and therefore will be sustainable because we can always continue using them.
Does that make sense?
Explanation:
If I c<span>onsider this northern site of primary succession following the retreat of a glacier, the characteristics that I would expect to see among the plant comprising the pioneer species are the processes of ecological succession and the primary succession.</span>
