**Core Concept**
Trichomonas vaginalis is a sexually transmitted protozoan parasite that causes trichomoniasis, a common vaginal infection in women and urethritis in men. The infection is characterized by an intense inflammatory response in the urogenital tract.

**Why the Correct Answer is Right**
The correct answer is related to the pathogenesis of trichomoniasis. Trichomonas vaginalis adheres to the epithelial cells of the urogenital tract through its surface glycoproteins and flagellum. The parasite then induces an intense inflammatory response by releasing various enzymes, including proteases and lipases, which damage the epithelial cells and lead to the release of pro-inflammatory cytokines.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Trichomonas vaginalis is not known to cause a significant decrease in the pH of the vagina.
**Option B:** This option is incorrect because the primary mode of transmission of Trichomonas vaginalis is through sexual contact, not through contaminated food or water.
**Option C:** This option is incorrect because while Trichomonas vaginalis can cause urethritis in men, it is not typically associated with epididymitis.

**Clinical Pearl / High-Yield Fact**
A diagnosis of trichomoniasis can be made using a wet mount preparation of vaginal discharge, which shows the characteristic motile flagellated protozoa.

**Correct Answer:** D.