Which of the following method is the best predictor for ovulation in a female infeility patient during a menstual cycle?

In an ovulatory cycle plasma progesterone reaches a peak of 15ng/ml at mid-luteal phase (22-23days). Basal body temparature (BBT) falls at the time of ovulation by about 1/2degree. During the progestational half of cycle temparature is slightly raised above the preovulatory level. But it is now obsolete because: 1. Tedious daily recording 2. Not very accurate 3. Better modalities are available In endometrial biopsy endometrium from the uterus is curetted preferably 1 or 2 days prior to the onset of menstruation. Histological examination done for secreatory changes. Now a days endometrial biopsy is omitted as a routine investigation of infeility. Only used in suspected tubercular endometritis Fern test: cervical mucus is examined under a low power microscope. During estrogenic phase it shows a characteristic fern patten which disappears after ovulation Reference: chapter 19; Infeilty and sterility; shaw's textbook of gynecology - 16th edition