Which of the following statements concerning the biochemical oxygen demand (BOD) is CORRECT?

A) It is a measure of the amount of oxygen in water.
B) It is proportional to how potable water is.
C) It is used as a bioreceptor index.
D) It is a measurement of the amount of oxygen that aerobic bacteria require to decompose organic wastes in water.
E) It is a filter system to purify drinking water.