Ans. C. The amount of the substance in the compartment does not change with respect to timeIn a steady state, the amount or concentration of a substance in a compartment does not change with respect to time. Although there may be considerable movements into and out of the compartment, there is no net gain or loss. Steady states in the body often do not represent an equilibrium condition, but they are displaced from equilibrium by the constant expenditure of metabolic energy.