The correct option is B
1 - GnRH, 2 - LH, 3 - Testosterone
Spermatogenesis is the process of production of sperms and it is under the control of hormones.
Hypothalamus secretes gonadotropin releasing hormone or GnRH at the time of puberty in males.
GnRH stimulates the anterior pituitary to produce two gonadotropins, luteinising hormone (LH) and follicle stimulating hormone (FSH).
LH or luteinising hormone is also called interstitial cell-stimulating hormone (ICSH). It stimulates Leydig cells of testes to produce testosterone and other androgens.
Testosterone supports the process of spermatogenesis. Hence option b is correct.
FSH or follicle stimulating hormone acts on Sertoli cells. Sertoli cells produce ABP and inhibin. ABP is an androgen binding protein which binds to testosterone and maintains high levels of androgens essential for spermatogenesis. Inhibin suppresses FSH synthesis.
FSH acts directly on spermatogonia to stimulate sperm production.