S₁: The houses in the Indus Valley were built of baked bricks.
P: This staircase sometimes continued upwards on to the roof.
Q: Access to the upstairs rooms was by a narrow stone staircase at the back of the house.
R: The drains were incorporated in the walls.
S: The houses had bathrooms and water closets, rubbish chutes and excellent drainage systems.
S₆: They led outside into covered sewers which ran down the side of the streets.

The Proper sequence should be:

A. PSQR

B. QPSR

C. QRPS

D. SPQR

Answer: Option B

Solution(By Examveda Team)

Access to the upstairs rooms was by a narrow stone staircase at the back of the house. This staircase sometimes continued upwards on to the roof. The houses had bathrooms and water closets, rubbish chutes and excellent drainage systems. The drains were incorporated in the walls.