**Core Concept**
The examination of a rape victim involves the assessment of the integrity of the hymen to determine if it has been ruptured and if the rupture is recent or old. This assessment is crucial in forensic medicine to establish the timeline of the sexual assault.

**Why the Correct Answer is Right**
The correct answer is **Option C: Hymenal colorimetry or Hymenal pH testing**. Hymenal colorimetry involves the comparison of the color of the hymenal tissue to that of the surrounding vaginal mucosa. A recent rupture will show a distinct color change due to the presence of blood. Hymenal pH testing measures the pH of the hymenal tissue, which is typically acidic in nature. A recent rupture will show a significant increase in pH due to the presence of blood and other cellular debris.

**Why Each Wrong Option is Incorrect**
**Option A:** Hymenal thickness measurement is not a reliable method for determining the age of a rupture. Hymenal thickness can vary greatly between individuals and can be influenced by various factors such as age, hormonal changes, and physical activity.
**Option B:** Hymenal examination under magnification or with a colposcope is useful for visualizing the hymenal tissue but does not provide information about the age of the rupture.

**Clinical Pearl / High-Yield Fact**
In forensic medicine, the presence of a ruptured hymen is not conclusive evidence of sexual assault, as the hymen can be ruptured due to various other causes such as physical activity, sports, or accidents.

**Correct Answer:** C. Hymenal colorimetry or Hymenal pH testing.