The correct option is B FSH
Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropins. This increases secretion of LH (luteinizing hormone) and FSH (follicle stimulating hormone). LH acts on leydig cells and stimulates synthesis and secretion of androgens, which in turn stimulates the process of spermatogenesis. FSH acts on sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis. So, the correct option is 'FSH'.