What is full form of BOD?

BOD stands for a measurement that tells us how much oxygen is needed by bacteria to break down organic matter in a water sample. Think of it like this: If there's lots of decaying plants or waste in the water, bacteria will need more oxygen to eat it all up.

Let's look at the options:

Option A: Biological Oxygen Deficit - This sounds close, but "deficit" means a shortage. BOD measures the amount of oxygen needed, not a shortage.

Option B: Biological Oxygen Difference - This doesn't really make sense in this context. We are measuring the oxygen needed for a specific process.

Option C: Biological Oxygen Demand - This is the correct answer! It perfectly describes the measurement of oxygen needed by bacteria to decompose organic material in water.

Option D: Biological Oxygen Distribution - This describes how oxygen is spread in the water, not the amount needed for decomposition.

Therefore, the full form of BOD is Biological Oxygen Demand.