Identify the sequence of processes in sewage treatment:

• A
  Filtration $\rightarrow$ Sedimentation $\rightarrow$ Biological treatment $\rightarrow$ Anaerobic sludge digesters
• B
  Sedimentation $\rightarrow$ Filtration $\rightarrow$ Biological treatment $\rightarrow$ Anaerobic sludge digesters
• C
  Filtration $\rightarrow$ Sedimentation $\rightarrow$ Anaerobic sludge digesters $\rightarrow$ Biological treatment
• D
  Sedimentation $\rightarrow$ Filtration $\rightarrow$ Anaerobic sludge digesters $\rightarrow$ Biological treatment