**Core Concept**
The development of the genital system is a complex process involving the formation of the gonads, ducts, and external genitalia. It is influenced by a delicate balance of genetic, hormonal, and molecular signals, which dictate the sex of the individual.

**Why the Correct Answer is Right**
The development of the genital system is initiated by the presence or absence of the SRY gene on the Y chromosome, which triggers the formation of testes in males. The testes then produce anti-Müllerian hormone (AMH), which causes the regression of the Müllerian ducts and the development of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles. In females, the absence of the SRY gene leads to the formation of ovaries, which produce estrogen and inhibit the development of the Wolffian ducts.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the role of the SRY gene in the development of the genital system.
**Option B:** This option is incorrect because it does not mention the importance of hormones in the development of the genital system.
**Option C:** This option is incorrect because it does not provide a clear explanation of how the sex of the individual is determined.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the development of the genital system is a complex process influenced by multiple genetic and hormonal factors. Abnormalities in this process can lead to disorders such as sex reversal, where an individual has both male and female reproductive organs, or intersex conditions, where an individual has reproductive organs that do not fit typical male or female anatomy.

**Correct Answer: D.**