According to the text, during the follicular phase, the secretion of gonadotropins (LH and FSH) increases, which stimulates the secretion of estrogens by the growing follicles. The text states that 'Both LH and FSH attain a peak level in the middle of cycle', resulting in the LH surge which 'induces rupture of Graafian follicle and thereby the release of ovum (ovulation)'. Biologically, the high concentration of estrogen produced by the mature follicle exerts positive feedback, triggering this LH surge. Among the given options, high estrogen is the correct condition preceding ovulation, whereas progesterone peaks later in the luteal phase.