Read the following passage to answer question.
One of the most important features of our closed material system is its degree of organization. Whereas the biosphere is an open system in terms of energy, constantly receiving solar rays, no new physical identity has been created since the birth of the planet. Thus, the recycling of everything is an absolute necessity to the nature of all ecological processes. The waste products of one process must become the materials of the next. Some of the more highly organized materials, such as fossil fuels, have taken millions of years to develop. These are nonrenewable resources — that is, once used, they cannot be replaced, at least in this geological age. In order to avoid entropy, materials cannot be used up faster than they are produced. In its simplest terms, then, pollution can be seen as our creation of more wastes than ecosystem can handle. We have interfered with nature's system of recycling and purification. The excess wastes we have produced are not being recycled and purified.
JENKINS-MURPHY, Andrews. How to prepare for the TOEFL. USA: HBJ, 1987.
Considering the vocabulary of the sentences,
