Use of chlorine in the treatment of sewage________?

Air vessel fitted to a reciprocating pump________?

Hydrogen ion concentration in distilled water is________?

Liquid delivery by centrifugal pump starts, only when the head developed by it is equal to the ________ head?

Which of the following fuel gases contains maximum amount of carbon monoxide?

Scouring is a finishing operation during the manufacture of fibre, which aims at ________ of fibres?