Answer:
animal wastes and fertilizers
Explanation:
The majority of the nitrates that are polluting the rivers come from the animal wastes and from the fertilizers used in the agriculture. The increased amounts of nitrates in the rivers causes eutrophication. This basically means that the water is becoming over-saturated with nutrients. This leads to the spreading out of the algae. As the algae spread out more and more, they cover the surface part of the water, so large portions of the rivers do not receive sunlight, which kills of the organisms that use photosynthesis. Further, the algae reduce the amount of oxygen in the water, often resulting in dying out of the fishes. It is a chain reaction that leads from one thing to another and the end result is devastating.
<h2>
short definition:</h2>
<u><em> a species is a population or groups of populations that can potentially interbreed freely within and among themselves.</em></u>
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<em><u> Subspecies, are subgroups within a species that have different traits </u></em>
<h2>
long definition</h2>
<em><u>A species is a group of organisms that (in the case of sexually reproducing organisms) can freely interbreed, producing fertile offspring. This definition has its problems, but overall, it encompasses the meaning of the word “species” in biology.</u></em>
<em><u></u></em>
<em><u>A subspecies is, as the name implies, a smaller population within a species that share a particular common trait. Usually a sub species is at least partially genetically isolated from it’s parent species, so that interbreeding is less likely to occur. Most often a sub species is physically separated from the rest of the species, and may have some specific physical differences from the rest of the species. However, they are still able to interbreed with members of the parent population.</u></em>
The answer to this question is the second item in the choices which is "where older buildings were built on a thick layer of sediment". We know that seismic vibration is the sound or movement generated from the ground. This happening is unwanted and cannot be controlled. Once this occurs in higher magnitude it would cause great damage to our structure were buildings made of rock collapse.
