Biochemical Oxygen Demand, (BOD) is a measure of organic material present in water. BOD value less than 5 ppm indicates a water sample to be________.

The correct option is A rich in dissolved oxygen.
BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria (those bacteria that live only in an environment containing oxygen). BOD is used, often in wastewater-treatment plants, as an index of the degree of organic pollution in water.

Clean water has a BOD which is less than 5 ppm. If it is equal to or more than 12 ppm, then the water is considerd as polluted. So, this indicates water rich in dissolved oxygen, helps the microorganisms to oxidize inorganic and organic materials.

BOD value less than 5 ppm indicates a water sample to be rich in dissolved oxygen. So, option (A) is correct.