Which of the following are concerned with thymus gland?
I. It is well-developed in new borns but reduces from adulthood to old age after sexual maturity.
II. It is located in the posterior portion of the root of the third ventricle.
III. It secretes hormone thymosin, which promotes immune competence in young T-lymphocytes.
IV. It functions as biological clock.
Choose the correct option.
A. I, II and III
B. II, III and IV
C. II and IV
D. I and III
