## Core Concept
The seminal fluid's composition is crucial for sperm function and fertility. Fructose in the seminal fluid provides energy for sperm motility. The **seminal vesicles** are responsible for producing a significant portion of the seminal fluid, including fructose.

## Why the Correct Answer is Right
The correct answer, **C. Seminal vesicle dysfunction**, is right because the seminal vesicles produce fructose, which is then secreted into the seminal fluid. This fructose serves as a nutrient for spermatozoa, supporting their motility and function. Absence of fructose in the seminal fluid would indicate that the seminal vesicles are not functioning properly or are absent.

## Why Each Wrong Option is Incorrect
* **Option A:** Prostate dysfunction - The prostate gland contributes to the seminal fluid but is not primarily responsible for fructose production. Its dysfunction might affect other components of the seminal fluid but not specifically fructose levels.
* **Option B:** Epididymal dysfunction - The epididymis is involved in sperm maturation and storage but does not produce fructose. Its dysfunction would more likely affect sperm quality rather than fructose levels in the seminal fluid.
* **Option D:** Testicular dysfunction - Testes produce sperm and hormones like testosterone but not fructose. Testicular dysfunction would primarily affect sperm production and hormone levels rather than fructose in the seminal fluid.

## Clinical Pearl / High-Yield Fact
Absent fructose in the seminal fluid, also known as **fructose-free semen**, is a diagnostic criterion for **seminal vesicle agenesis or obstruction**. This condition can be a cause of male infertility. A simple diagnostic test is to check the seminal fluid for fructose; its absence prompts further investigation into seminal vesicle function or anatomy.

**Correct Answer: C. Seminal vesicle dysfunction**