**Core Concept**
The question is testing the understanding of the mechanism behind opioid-induced nausea and vomiting. This phenomenon is a result of the activation of specific receptors in the brainstem by opioid analgesics, which leads to the stimulation of the vomiting center.

**Why the Correct Answer is Right**
The correct answer is related to the activation of the chemoreceptor trigger zone (CTZ) in the area postrema of the brainstem. The CTZ is sensitive to opioids, and their binding to the mu-opioid receptors in this area triggers the release of neurotransmitters such as dopamine, substance P, and acetylcholine, which ultimately leads to the stimulation of the vomiting center. This results in the characteristic nausea and vomiting associated with opioid administration.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism behind opioid-induced nausea and vomiting.
**Option B:** This option is incorrect because it is not directly related to the vomiting center or the CTZ in the brainstem.
**Option C:** This option is incorrect because it is more related to the anticholinergic side effects of opioids, such as dry mouth and constipation, rather than nausea and vomiting.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that opioid-induced nausea and vomiting can be prevented or treated with antiemetic medications such as ondansetron, which are selective serotonin 5-HT3 receptor antagonists.

**Correct Answer:** C.