The most commonly used sewer under culverts is A. Circular brick sewer B. Circular cast iron sewer C. Semi-elliptical sewer D. Horseshoe type sewer

The most commonly used sewer under culverts is a circular cast iron sewer. This type of sewer is strong and durable, and it can withstand the weight of the culvert and the traffic that passes over it. It is also relatively easy to install and maintain.

Circular brick sewers are also strong and durable, but they are more difficult to install and maintain. Semi-elliptical sewers are less strong than circular sewers, and they are more likely to leak. Horseshoe type sewers are the weakest type of sewer, and they are not commonly used.

Here is a more detailed explanation of each type of sewer:

• Circular brick sewers are made of bricks that are laid in a circular pattern. They are strong and durable, but they are more difficult to install and maintain than other types of sewers.
• Circular cast iron sewers are made of cast iron pipes that are joined together to form a circular pipe. They are strong and durable, and they are relatively easy to install and maintain.
• Semi-elliptical sewers are made of two semi-elliptical pipes that are joined together to form a complete pipe. They are less strong than circular sewers, and they are more likely to leak.
• Horseshoe type sewers are made of a single piece of cast iron that is shaped like a horseshoe. They are the weakest type of sewer, and they are not commonly used.