Pick up the correct statement from the following: A. The boning rod is used for checking the levels of the sewer inverts B. Manhole covers are made circular for the convenience of the cleaning staff C. A manhole is classified as shallow manhole if its depth is less than 0.9 m D. All the above

The correct answer is D. All the above.

A boning rod is a tool used to check the levels of the sewer inverts. It is a long, thin rod with a pointed end. The rod is inserted into the sewer pipe and the level is checked by looking at the mark on the rod that lines up with the sewer invert.

Manhole covers are made circular for the convenience of the cleaning staff. The circular shape allows the manhole cover to be easily lifted and replaced.

A manhole is classified as shallow manhole if its depth is less than 0.9 m. This is because shallow manholes are easier to access and clean than deeper manholes.

Here are some additional details about each option:

• A boning rod is a tool used to check the levels of the sewer inverts. It is a long, thin rod with a pointed end. The rod is inserted into the sewer pipe and the level is checked by looking at the mark on the rod that lines up with the sewer invert. The sewer invert is the lowest point in the sewer pipe. It is important to check the levels of the sewer inverts to make sure that they are correct. If the levels are not correct, it can cause problems with the flow of sewage.
• Manhole covers are made circular for the convenience of the cleaning staff. The circular shape allows the manhole cover to be easily lifted and replaced. Manhole covers are also made of heavy materials, such as cast iron, to prevent them from being stolen or damaged.
• A manhole is classified as shallow manhole if its depth is less than 0.9 m. This is because shallow manholes are easier to access and clean than deeper manholes. Shallow manholes are typically used in residential areas, while deeper manholes are used in commercial and industrial areas.