**Core Concept**
Ovulation is a critical phase in the menstrual cycle, marking the release of an ovum from the ovary. It is essential to diagnose ovulation accurately for fertility assessment, family planning, and management of reproductive disorders. The best diagnostic methods should ideally provide a clear indication of the timing of ovulation.

**Why the Correct Answer is Right**
The most reliable method for diagnosing ovulation is by detecting the luteinizing hormone (LH) surge using urinary LH assays or home ovulation prediction kits. These tests are based on the principle that the LH surge triggers ovulation. The LH surge typically occurs 24-48 hours before ovulation, making it an excellent indicator of impending ovulation. This surge is caused by the release of GnRH from the hypothalamus, which stimulates the pituitary gland to release LH.

**Why Each Wrong Option is Incorrect**
**Option A:** Basal body temperature (BBT) measurement is not a reliable method for diagnosing ovulation. Although BBT increases after ovulation due to the production of progesterone, this change is not consistent or specific enough to serve as a diagnostic marker.
**Option B:** Ultrasound examination of the ovaries can detect the presence of a dominant follicle, but it does not necessarily confirm ovulation. In addition, ultrasound is not suitable for daily monitoring of ovulation.
**Option C:** Pelvic examination is not a practical method for diagnosing ovulation. While it can provide information about the presence of a corpus luteum, it is not specific or sensitive enough for this purpose.

**Clinical Pearl / High-Yield Fact**
The LH surge is a critical event in the menstrual cycle, and its detection is essential for diagnosing ovulation. Remember that LH assays are more sensitive and specific than BBT measurements or pelvic examinations for detecting ovulation.

**Correct Answer: C. Ultrasound examination of the ovaries can detect the presence of a dominant follicle, but it does not necessarily confirm ovulation. In addition, ultrasound is not suitable for daily monitoring of ovulation.