Inter-distance between ventilation columns in a sewer line is kept A. 25 to 50 m B. 50 m to 100 m C. 100 m to 150 m D. 150 m to 300 m

The correct answer is: B. 50 m to 100 m

Ventilation columns are used to provide ventilation to sewer lines. They help to prevent the build-up of gases and odors, and they also help to prevent the sewer line from collapsing. The inter-distance between ventilation columns is typically kept between 50 m and 100 m. This is to ensure that the columns are evenly spaced and that they provide adequate ventilation to the sewer line.

Option A is incorrect because it is too short. The inter-distance between ventilation columns should be at least 50 m to ensure that they are evenly spaced and that they provide adequate ventilation to the sewer line.

Option C is incorrect because it is too long. The inter-distance between ventilation columns should be no more than 100 m to avoid unnecessary costs and to ensure that they are evenly spaced.

Option D is incorrect because it is not a realistic option. The inter-distance between ventilation columns should be no more than 100 m to avoid unnecessary costs and to ensure that they are evenly spaced.