[单选题]
2. Which statement best describes 4hv-;wepss g+ j c6o:d 8m1dpihomeorm 8rpj1v xz,xk8t8n3stasis?
A. Keeping constant conditions.
B. Excretion of unwanted substances.
C. Maintaining internal conditions in a constant state.
D. Maintaining internal conditions within set limits.