A  river is the source of water for water supply to a town. Its water is very turbid and polluted. The correct sequence of steps for treating the river water would be

presedimentation $\to$ prechlorination $\to$ coagulation $\to$ sedimentation $\to$ filtration $\to$ post-chlorination

coagulation $\to$ sedimentation $\to$ post-chlorination

coagulation $\to$ filtration $\to$ sedimentation $\to$ post-chlorination

sedimentation $\to$ post-chlorination