What does $STPs$ stand for?

The major contribution of bacteria in the carbon cycle includes ..........

Statement $S$: In the primary stage of sewage treatment,physical particle matter is removed from water through filtration and sedimentation.
Reason $R$: Through sedimentation,soil or small pebbles are removed.

What happens to activated sludge?

Statement $P$: $A$ major portion of organic matter in water is consumed by chemical processes.
Statement $Q$: Microorganisms,including bacteria,consume organic matter present in water.

Select the correct statement from the following: