Answer
(b)
Work Step by Step
Lakes located near agricultural fields in temperate ecosystems are most likely to experience the highest biochemical oxygen demand during the spring. This is because in the spring, the agricultural fields are often fertilized, leading to runoff of excess nutrients (such as nitrogen and phosphorus) into the lakes.
This excess nutrient runoff promotes rapid algal growth in the lakes, and when these algae die and decompose, they consume a significant amount of dissolved oxygen, leading to an increase in biochemical oxygen demand.
The answer is (b).
