Q1: The spacing of bars of perforations of fine screens used for the treatment of sewage, is

ANS:A - 2 to 3 mm

The spacing of bars or perforations of fine screens used for the treatment of sewage typically ranges from 2 to 3 mm. These fine screens are designed to remove smaller suspended solids, debris, and particles from wastewater before it undergoes further treatment processes. The narrow spacing of bars or perforations allows for efficient filtration of fine particles while preventing larger objects from passing through. Therefore, the correct option is: a. 2 to 3 mm