Design Of Sewer

Step 1: Setting sight rails.
The first step is to establish reference sight rails above the trench (B).

Step 2: Driving pegs.
Next, pegs are driven to the level of the invert line of the sewer (C).

Step 3: Transferring center line.
The sewer's center line is then transferred to the bottom of the trench (A).

Step 4: Placing sewer.
Finally, the sewer is placed in the trench (D).

Step 5: Conclusion.
Thus, the correct sequential order is B → C → A → D. Hence, the correct answer is (D).