Which of the following best characterizes the factors that have contributed to the "dead zone" in the waters of the chesapeake bay for the past few decades?
a. fertilizer runoff from farms, animal manure, and stormwater runoff.
b. increasing oil spills in the chesapeake bay.
c. gasoline spillage from the refineries.
d. the farm practices around the chesapeake bay.

A. fertilizer runoff from farms, animal manure, and stormwater runoff.

Explanation:

Agriculture and Urbanization are the main factors responsible for the “dead zone” in the waters of the Chesapeake Bay.  

In the eastern part of the Chesapeake Bay, you have agricultural activities such as the poultry farms which produce huge amounts of manure that are later washed through runoff into the bay. Also, nitrogen from the use of fertilizers in the farmlands are being washed along into the bay leading to increased level of nitrogen in the waters which reduces the availability of oxygen in the bay. The level of oxygen in the bay is reduced as the excess nutrients that are washed into the bay causes an overgrowth of algae, which later sinks and decompose in the water.  

There are many factories located by the western part of the bay where there is also the concentration of urban centers. Much nitrogen is released into the air, which later ends up in the bay.  

As a result of urbanization, large volume of water is created in the form of stormwater runoff, as rain falls on driveways, rooftops, roads and other pavement, making  difficult for the water to be absorbed into the ground. This large volume of water moves quickly into the bay. Many pollutants such as nitrogen, bacteria, pesticides, trash etc, are washed along into the bay.