Answer is: B. Energy transfer would occur between the copper bars and the surroundings.
Closed system is a physical system that does not allow transfer of mass and energy in or out of the system.
Open system is a physical system that does allow transfer of mass and energy in or out of the system, have input and output flows.
Thermal conductuction 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.