Q1: The minimum diameter of a sewer is kept

ANS:B - 15 cm

The minimum diameter of a sewer is typically kept at 10 cm (centimeters). This diameter ensures that the sewer pipe can effectively transport wastewater and solids without becoming easily blocked or overwhelmed. Larger diameters may be used depending on factors such as the expected flow rate and the specific requirements of the sewer system, but 10 cm is a common minimum diameter for sewer pipes in residential and small-scale applications.