The correct option is D A – 4, B – 1, C – 2, D – 5, E – 3
GnRH is a hypothalamic hormone. The increased levels of GnRH then acts at the anterior pituitary gland and stimulates secretion of two gonadotropins – luteinising hormone (LH) and follicle stimulating hormone (FSH). The sperm head contains an elongated haploid nucleus, the anterior portion of which is covered by a cap-like structure, the acrosome. The acrosome is filled with enzymes like lysins that help in penetrating the layers around the ovum during fertilisation. During the follicular phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation. These changes in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones. The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles. Leydig cells secrete testosterone that stimulates spermatogenesis. Relaxin hormone is secreted only during pregnancy by the placenta. This hormone is also secreted by the corpus luteum of pregnancy, and loosens the connective tissue between the pelvic bone, which softens and relaxes the pelvic ligaments thereby widening the cervix. All these changes help accommodate the growing baby.