Select the correct sequence of events in a sewage treatment process.

A.   Passage of primary effluent into large aeration tanks for mechanical agitation and pumping of air.

B.   Passage of effluent into the settling tank and formation of activated sludge.

C.   Physical removal of particles through filtration and sedimentation.

D.  Release of effluent from the secondary treatment plant into natural water bodies.

E.    Growth of useful aerobic microbes into flocs which significantly reduce the BOD.