The main reason for making the cover of a vacuum flask airtight is to prevent heat loss by? by Sunday | Nov 16 | Physics JAMB | 0 comments A. convection B. conduction C. radiation D. evaporation Correct Answer: Option A – convection Users Also Read These:In a good thermos flask; the main cause of heat loss is?The vacuum between the double walls of a thermos…Which of the following factors should be considered…The inside of a vacuum flask is usually coated with…The main reason for establishing game reserves is to…