Read the Following Scenario and Answer the Question Below

Read the following scenario and answer the question below.
Glass Lake, located in a valley in low forested mountains, for many decades of the 19th and early 20th centuries was a favorite picnic, recreation, and fishing site for people in surrounding towns and farms. However, in the middle of the 20th century, a trend began in which the privately-owned farms in the Lakeʹs watershed were purchased by large agribusinesses.
The decision was made to grow a profitable crop. The demand for quality farmland resulted in the sale of most of the family-owned establishments and a large increase in the area of land under cultivation. Most of the forests were cut to acquire the land needed for crops. The use of chemical fertilizers and pesticides increased several fold by the end of the century. In addition, the combined population of the lakeside villages quadrupled during the same time. The lake experienced a slow degradation of water quality and biodiversity. Sport fishing declined and the lake became murky while the sediments in the lake increased in depth.
-A water quality expert checked the level of dissolved oxygen in lake water and found it .

A) was within normal limits for an unpolluted lake
B) very low at the surface and normal near the bottom sediments
C) was low-normal on the surface but extremely low near the bottom sediments
D) absent entirely
E) was much higher than normal