**Core Concept**
Anatomical differences between males and females are essential knowledge for medical students, especially in understanding the variations that can impact diagnosis and treatment. The question is asking about a specific structure present in males but not in females.

**Why the Correct Answer is Right**
The correct answer, **D. Prostate**, is a gland located in males that plays a crucial role in urine flow and contributes to semen production. It is not present in females, which is why it is the correct answer.

**Why Each Wrong Option is Incorrect**
A. **Option A. Ovaries**: Although ovaries are present in both males and females, the question specifically targets a structure unique to females. Ovaries are involved in female reproduction, whereas the correct answer, prostate, is specifically male.

B. **Option B. Fallopian tubes**: Although present in both sexes, the question targets a structure specific to the female reproductive system. The fallopian tubes are essential for fertilization and egg transport in females, while the prostate is of relevance to the male reproductive system.

C. **Option C. Vagina**: Similar to options A and B, the vagina is a structure specific to the female reproductive system. It is absent in males, making it incorrect in this context.

**Clinical Pearl / High-Yield Fact**
Understanding the differences between male and female anatomy is fundamental for accurate diagnosis and treatment. The presence of the prostate in males can help differentiate between male and female reproductive systems when examining patients.

**Correct Answer:** Prostate