[单选题]
3. Which of the foll nruo+se76+9h p;pb rg+ *vlvhowing are involved in thermoregulation in a mazvp zn.n3-np.vsvvp o.ci 0v)g) 78qvmmal?
I. The hypothalamus.
II. Skin thermoreceptors.
III. Pituitary gland.
IV. Thyroxin.
A. I and II only
B. II, III and IV only
C. All of the above
D. I, II and III only
