**Core Concept**
The question is testing knowledge of synthetic opioids, a class of potent analgesics used for pain management. Synthetic opioids are designed to mimic the effects of natural opioids, such as morphine, but with varying potencies and side effect profiles.

**Why the Correct Answer is Right**
The correct answer is fentanyl, a synthetic opioid with a potency 50-100 times greater than morphine. Fentanyl works by binding to opioid receptors in the brain and spinal cord, primarily through interaction with the mu-opioid receptor. This binding activates G-protein coupled receptors, leading to a decrease in the release of pain neurotransmitters such as substance P and glutamate.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a synthetic opioid, making it an incorrect choice.
* **Option B:** This option is not a potent opioid, and its pharmacological profile does not match that of a synthetic opioid.
* **Option C:** This option is not a synthetic opioid, and its potency is not comparable to fentanyl.

**Clinical Pearl / High-Yield Fact**
Fentanyl's potency can lead to rapid respiratory depression, making it essential to use it with caution and in controlled settings, such as in hospital ICUs or by experienced anesthesiologists.

**Correct Answer: C. Fentanyl**