(A) the softest layer of rock?
Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both.
Eutrophication can be a natural process in lakes, occurring as they age through geological time.
Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-20th century.
Human activities can accelerate the rate at which nutrients enter ecosystems.
The three observations that could help an individual in distinguising whether the organism is a fish or not is that it should live under water as fish can't survive without water, another thing is that it should laid eggs when it comes to giving birth because when it does not lay eggs but produces a living organism normally without an egg, it is considered to be a mammal and lastly, the appearance it possess such as having gils or fins.
Viscosity refers to the speed at which a substance can flow (i.e. the thickness of the substance/its ability to flow). I think that's the closest the English language gets.
