What is the advantage of designing a thermos so that it has a vacuum layer surrounding the area where hot liquids are stored?

Sorry i don’t know what to do

An atom's smaller negative particles are at a distance from the central positive particles, so the negative particles are easier to move. 

Answertechnician (a) is correct;

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other