Pick out the wrong statement.

• Biological oxygen demand (BOD) is a characteristic and not a constituent of water.
• BOD is a measure of the amount of oxygen which will be demanded & used in 5 days by the biological decomposition of the organic matter present in water stream present as food for the living organism.
• BOD is expressed in mg/litre (typically, BOD=2.5 mg/litre for potable water).
• none of these