Answer is: C) There is no air between the two flasks.
Heat in this example can transfer throw thermal conduction.
Because there are no mo molecules to transfer heat, there is no conduction.
Thermal conduction is the transfer of heat through physical contact. Thermal conduction is the transfer of heat by microscopic collisions of particles. Heat spontaneously flows from a hotter to a colder body.
The process of heat conduction depends on four basic factors: the temperature gradient, the cross section of the materials involved, their path length and the properties of those materials.
Because there are no mo molecules to transfer heat, there is no conduction.
