BOD is a measure of

• A

  ozone depletion in the stratosphere due to too many free radicals.
• B

  suspended particulate matter in the air causing lung problems.
• C

  pesticides which are non-biodegradable in the soil and water.
• Correct answer
  D

  organic material present in water needing dissolved oxygen to break them down depleting oxygen content in water.

Hence, the correct answer is option: 'D'.