The correct answer is B. Circular section.
A circular section is the most suitable section of sewer in a separate sewage system because it has the least amount of surface area to volume ratio. This means that it is the most efficient shape for carrying wastewater. Additionally, a circular section is the strongest shape for a sewer, which makes it less likely to collapse.
A rectangular section is not as efficient as a circular section because it has a larger surface area to volume ratio. This means that it is more likely to clog and more difficult to clean. Additionally, a rectangular section is not as strong as a circular section, which makes it more likely to collapse.
A standard form of egg shaped sewer is not as efficient as a circular section because it has a larger surface area to volume ratio. Additionally, a standard form of egg shaped sewer is not as strong as a circular section, which makes it more likely to collapse.
A modified egg shaped section is not as efficient as a circular section because it has a larger surface area to volume ratio. Additionally, a modified egg shaped section is not as strong as a circular section, which makes it more likely to collapse.