Q1: The drop man holes are generally provided in sewers for

ANS:C - hilly town ships

Drop manholes are generally provided in sewers for hilly townships. Hilly townships often have varying topography with steep gradients and changes in elevation. Drop manholes are designed to accommodate these changes by providing a vertical drop or step in the sewer line. They help manage the difference in elevation between two sewer sections while maintaining the required slope for proper flow and drainage. In hilly areas, drop manholes serve to prevent excessive excavation or grading of the terrain, as well as to ensure efficient sewage conveyance despite the challenging topography. They are strategically placed at points where the sewer line encounters significant changes in elevation or gradient. In contrast, in flat or plain areas, the terrain is generally uniform, and there may be less need for drop manholes since the sewer lines can maintain a more consistent slope without the need for vertical drops. Therefore, drop manholes are particularly useful and commonly provided in sewers for hilly townships where the terrain poses challenges to maintaining a continuous and uniform sewer gradient.