The Chesapeake Bay, which is along the coast of the Eastern U. S., is the largest estuary in the country. Many rivers, including the Potomac, empty into this section of the Atlantic Ocean.

During the 1970s, areas of the bay were found to have low levels of oxygen and could not support life. What was the cause of this problem?
A.
A non-native species of fish was introduced into the bay and killed all of the native species.
B.
People removed too many fish from the bay by over-fishing, and the ecosystem never recovered.
C.
High levels of nitrogen and phosphorus from agricultural runoff, sewage, and industrial pollution were flowing into the bay.
D.
The rivers stopped flowing into the bay, and it caused it to dry up and kill the fish.