Sewer manholes are generally provided at A. The change of gradient B. The change of direction C. The junctions of sewers D. All of these

The correct answer is D. All of these.

Sewer manholes are provided at the following locations:

• At the change of gradient: This is to ensure that the flow of sewage is smooth and does not cause any blockages.
• At the change of direction: This is to allow for the inspection and maintenance of the sewer line.
• At the junctions of sewers: This is to allow for the connection of different sewer lines.

Sewer manholes are an important part of the sewer system. They provide access to the sewer line for inspection and maintenance. They also help to prevent blockages and flooding.