Name the parts a, b, c and d.

Explanation

(a) A - Hypothalamus,
B - Anterior pituitary,
C - Sertoli cells,
D - Testosterone,
E - Negative feedback.
(b) Testosterone, in the connective tissue between seminiferous tubules of testes.
( c) FSH, LH secreted by pituitary control male sex hormone testosterone, which in turn controls level of GnRH in blood and GnRH controls amount of FSH and LH.
(d) (d) By negative feedback mechanism.