What is one effect of modern agricultural practices? 

A)  increase in genetic diversity through use of monocultures 
B)  prevention of soil erosion and desertification 
C)  benefits to human health from drinking groundwater with nitrates 
D)  contamination of recreational waters with livestock wastes

What does the hydrologic cycle reference?

A) seawater that is drawn into mid-ocean ridges, heated, and rises to the surface
B) water that is heated by magma and rises in hot springs
C) the rising and falling of tides in a cyclical manner
D) the way water is used to generate electrical energy
E) none of these