The correct answer is: A. Cast iron sewers.
Cast iron sewers are the most common type of sewer used for non-scouring velocities of 5 m/sec. They are made of cast iron, which is a strong and durable material that can withstand the high velocities of wastewater. Cast iron sewers are also relatively easy to install and maintain.
Cement concrete sewers are another type of sewer that can be used for non-scouring velocities of 5 m/sec. However, they are not as common as cast iron sewers because they are more expensive to install and maintain.
Glazed bricks sewers are not a good choice for non-scouring velocities of 5 m/sec because they are not as strong as cast iron or cement concrete sewers. They are also more likely to crack and leak.
Stone ware sewers are also not a good choice for non-scouring velocities of 5 m/sec because they are not as strong as cast iron or cement concrete sewers. They are also more likely to crack and leak.
In conclusion, cast iron sewers are the best type of sewer to use for non-scouring velocities of 5 m/sec. They are strong, durable, and easy to install and maintain.