The correct answer is B) atmosphere as heat. In a hydraulic system, energy losses occur due to factors such as friction in the fluid, bends/restrictions in the piping, and other sources of resistance. These energy losses are ultimately dissipated as heat, which is absorbed by the atmosphere surrounding the hydraulic system. The reservoir, piping, and other components do not absorb this heat energy; instead, it is released into the environment as waste heat. The other options are incorrect because the reservoir expansion chamber (A) is not the final destination of the energy losses, the piping flexibility (C) does not absorb the energy, and the fluid itself (D) is the source of the friction losses, not the final absorber of the energy.