Arrange the steps in a sequence for the removal of microorganisms during the purification of drinking water.
(a) Lime feeder
(b) Mechanical mixing
(c ) Alum feeder
(d) Sedimentation tank
(e) Passing through gravel and sand
(f) Chlorine feeder

Options

A. c a b d e f
B. c b a d e f
C. e a b c f d
D. a b d c e f

Explanation

To arrange the steps for the removal of microorganisms during the purification of drinking water, we can follow these steps in sequence:

1. **Mechanical Mixing (b)**: The first step involves mixing the water mechanically to ensure that any added chemicals, such as coagulants, are evenly distributed throughout the water.

2. **Alum Feeder (c)**: After mixing, alum (aluminum sulfate) is added to the water. This coagulant helps to clump together small particles and microorganisms, making them easier to remove.

3. **Lime Feeder (a)**: Lime is added next to adjust the pH of the water and further aid in the coagulation process. It helps in the formation of larger flocs that can settle more easily.

4. **Sedimentation Tank (d)**: The water then flows into a sedimentation tank where the heavier flocs settle to the bottom due to gravity, leaving clearer water on top.

5. **Passing Through Gravel and Sand (e)**: The water is then passed through layers of gravel and sand which act as a filter to remove any remaining particles and microorganisms.

6. **Chlorine Feeder (f)**: Finally, chlorine is added to disinfect the water, killing any remaining microorganisms and ensuring that the water is safe for drinking.

### Final Sequence:
1. Mechanical Mixing (b)
2. Alum Feeder (c)
3. Lime Feeder (a)
4. Sedimentation Tank (d)
5. Passing Through Gravel and Sand (e)
6. Chlorine Feeder (f)