56. What happens when the water table drops below sea level in aquifers near the ocean?  

68. What is the major cause of ocean acidification?  

71. What effect do acidic ocean waters have on shells made of calcium carbonate?  

42. Tiny bits of plastic gather in specific areas of the world’s oceans where strong currents circle around areas with very weak, or even no, currents. These regions are called:  

46. Americans produce _____ amount of solid waste produced by most less-developed countries.  

66. The Mississippi River watershed includes land area from:  

34. The ozone layer is located in the:  

67. What was the dramatic event that helped spur passage of the 1972 Clean Water Act?  

40. Which was the first environmental law that required the U.S. government to consider environmental issues before approving policies?  

33. How can consumers influence businesses to be more environmentally sustainable?