Study the given figure showing how water is made pure before it reaches our home and identify P, Q, R and S.
| P | Q | R | S | |
| A | Mixing tank | Pump | Settling tank | Filter |
| B | Pump | Mixing tank | Settling tank | Filter |
| C | Pump | Settling tank | Mixing tank | Filter |
| D | Filter | Mixing tank | Settling tank | Pump |