What is a possible answer to a scientific question, based on evidence that can be tested by observation or
experimentation?

A hypothesis is a possible explanation for a set of observations or an answer to a scientific question. A hypothesis must be testable and measurable. This means that researchers must be able to carry out investi- gations and gather evidence that will either support or disprove the hypothesis.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.