Answer:
OB. Energy transfer would occur between the copper bars and the surroundings.
Step-by-step explanation:
We define an isolated system as a system in which there is neither exchange of material nor energy while an open system is one in which materials and energy can be exchanged with the environment.
Given an open system consisting of two copper bars at different temperatures, energy will not only be exchanged between the copper bars but also between the copper bars and the environment.