A wastewater sample has a 5-day Biochemical Oxygen Demand (BOD5) of 250 mg/L and a Chemical Oxygen Demand (COD) of 400 mg/L. Based on the BOD5/COD ratio, the wastewater is classified as:

Prolonged exposure to extreme cold temperatures may result in tissue damage known as frostbite, which is categorized as a:

In the context of ecosystem energy dynamics, which of the following expressions correctly defines Net Primary Productivity (NPP)?