## **Core Concept**
The composition of semen involves contributions from multiple male reproductive organs. Semen is a complex fluid that provides the medium for sperm transport and survival. The major contributors to semen include the testes, epididymis, seminal vesicles, prostate gland, and bulbourethral glands.

## **Why the Correct Answer is Right**
The correct answer, **seminal vesicles**, is right because these glands contribute significantly to the volume and composition of semen. Seminal vesicles produce a substantial portion of the fluid that makes up semen, contributing about 50-60% of the total seminal fluid volume. This fluid is rich in **fructose**, which serves as an energy source for sperm, and other substances that help in sperm function and survival.

## **Why Each Wrong Option is Incorrect**
- **Option A: Testes**. While the testes produce sperm, they contribute only a small volume to the seminal fluid, not the major portion.
- **Option B: Epididymis**. The epididymis stores and matures sperm but does not contribute significantly to the seminal fluid volume.
- **Option C: Prostate gland**. Although the prostate gland does contribute to semen, producing about 20-30% of the seminal fluid, its contribution is not as significant as that of the seminal vesicles. The prostate's secretions help nourish the sperm and make up a significant part of the fluid but are not the major contributor.
- **Option D: Bulbourethral glands**. These glands contribute a small amount of clear fluid to semen but are not the major contributors.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **seminal vesicle dysfunction or absence** can lead to **aspermia** or significantly reduced ejaculate volume, highlighting the crucial role of seminal vesicles in semen production.

## **Correct Answer:** C. Seminal vesicles.