Each Summer, a Large ʺDead Zoneʺ Devoid of Fish and Other

Multiple Choice

Each summer, a large ʺdead zoneʺ devoid of fish and other animals develops where the Mississippi River flows into the Gulf of Mexico. What causes this?

A) Large quantities of fertilizer run off from Midwestern farm fields into the Mississippi River.
B) Acid rain makes the gulfʹs water too acidic to support fish.
C) High levels of pesticides are used in the Mississippi River basin.
D) There are high levels of mercury in the river water.
E) Global warming is making the river water too hot for the fish to tolerate.