**Core Concept**
The process of erection of the penis involves the integration of neural, vascular, and hormonal signals. The parasympathetic nervous system plays a crucial role in initiating and maintaining erection through the release of neurotransmitters such as nitric oxide and acetylcholine. The involvement of specific nerves in this process is essential for understanding the physiology of erection.

**Why the Correct Answer is Right**
The correct answer involves identifying the nerve that is not directly involved in the process of erection. The parasympathetic nerves, specifically the pelvic splanchnic nerves (S2-S4) and the cavernous nerves, are responsible for transmitting signals that lead to erection. The cavernous nerves release nitric oxide, which causes relaxation of the smooth muscle in the corpus cavernosum, leading to increased blood flow and erection. In contrast, the hypogastric nerves are sympathetic nerves that are involved in ejaculation and detumescence (the process of returning to a flaccid state).

**Why Each Wrong Option is Incorrect**
* **Option A:** The pudendal nerve is involved in the innervation of the external genitalia, including the penis, and plays a role in erection and ejaculation.
* **Option B:** The dorsal nerve of the penis is responsible for transmitting sensory information from the penis and is involved in the process of erection.
* **Option C:** The cavernous nerves are directly involved in the process of erection and are responsible for releasing nitric oxide, which causes relaxation of the smooth muscle in the corpus cavernosum.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the cavernous nerves are at risk during radical prostatectomy, a surgical procedure for prostate cancer, which can lead to erectile dysfunction in some patients.

**Correct Answer: D. Hypogastric nerves.**