A/C/D: All of these answers are positive effects, of human water use.
By process of elimination it must be (B) Also the run off is basically stripping the soil of the nutrients a farmer would need to grow crops, so this is incredibly bad - but a problem easily fixed.
Out of the choices given, the best one to describe the negative impact of human water use is the increased runoff carries fertilizers to other parts of land. The rest of the choices are all positive impacts of human water use. The correct answer is B.
