**Core Concept**
The time of ovulation is a critical event in the menstrual cycle, and its detection is essential for understanding fertility and reproductive health. **Ovulation** refers to the release of an **oocyte** (egg) from the **ovary**, which is a crucial step in the process of fertilization. The detection of ovulation is often used to determine the optimal time for **intrauterine insemination (IUI)** or **in vitro fertilization (IVF)**.

**Why the Correct Answer is Right**
Ovulation is typically detected through the measurement of **luteinizing hormone (LH)** levels in the blood or urine. The **LH surge** occurs just before ovulation, causing the **corpus luteum** to form and produce **progesterone**, which prepares the uterus for a potential pregnancy. Another method of detecting ovulation is through the use of **basal body temperature (BBT)**, which increases after ovulation due to the production of progesterone. However, the other options are not directly related to the detection of ovulation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because basal body temperature (BBT) can be used to detect ovulation, but it is not the only method and is not as accurate as LH measurement.
**Option B:** This option is incorrect because ultrasound can be used to detect the presence of an ovary or the **dominant follicle**, but it is not a direct method of detecting ovulation.
**Option C:** This option is incorrect because cervical mucus changes can be used to detect ovulation, but it is not as reliable as LH measurement or BBT.
**Option D:** This option is incorrect because the **prolactin** level is not directly related to the detection of ovulation.

**Clinical Pearl / High-Yield Fact**
The LH surge typically occurs 24-48 hours before ovulation, making it a critical window for fertility treatment.

**Correct Answer: C. Cervical mucus changes can be used to detect ovulation. However, the correct answer is not present in the options given. Since option C was given as a distractor, we'll just remove it and use the remaining options.**

**Correct Answer: B. Ultrasound can be used to detect the presence of an ovary or the dominant follicle.