**Core Concept**
Bilateral vasectomy is a surgical procedure that obstructs the vas deferens, preventing the release of sperm into the semen. This leads to a deficiency in a specific substance essential for the formation of semen.

**Why the Correct Answer is Right**
After bilateral vasectomy, the deficiency seen is in fructose. This is because the vas deferens contains fructose, which is a sugar molecule that plays a crucial role in sperm motility and the formation of semen. However, fructose is also produced by the seminal vesicles. The absence of sperm in the semen after vasectomy is not due to fructose deficiency as the seminal vesicles continue to produce fructose. The correct answer is related to the substance produced by the seminal vesicles.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not related to the deficiency seen after bilateral vasectomy.
* **Option B:** While the vas deferens does contain fructose, the correct answer is related to the substance produced by the seminal vesicles.
* **Option C:** This option is not directly related to the effects of bilateral vasectomy on semen composition.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that bilateral vasectomy affects the vas deferens, but the seminal vesicles continue to produce fructose, which is present in the semen.

**Correct Answer: B. Fructose**