Answer Choice C vs. E

First of all, complaints are often based on subjective feelings, and not on actual numbers: some people complain about the tiniest of things and some complain only about huge things. Pollution could improve (or get worse), and more (or fewer) people file complaints. Also, there could be an infininte number of reasons that people stop filing complaints. Here are a few: 1) Government policy has made it more difficult to file complaints, so people don't bother anymore. 2) People have become accustomed to the levels of pollution and don't really notice it anymore. 3) The people who were filing complaints in the past have already filed so many complaints and received no response that they're sick of filing complaints. If it's not going to work, why bother? 4) The people who would have complained have left the area and the population has seen a decrease, or non-complainers have moved in to take their place.