**Core Concept**
Opium poisoning is a clinical scenario that involves the systemic effects of opioids, which are a class of substances that act on the central nervous system to produce analgesia, sedation, and respiratory depression. The pupil condition in opium poisoning is an important clinical finding that can help in diagnosing and managing the condition.

**Why the Correct Answer is Right**
In opium poisoning, the pupils typically constrict due to the stimulation of the mu-opioid receptors in the spinal cord and the brainstem. The activation of these receptors leads to an increase in the release of acetylcholine, a neurotransmitter that stimulates the muscarinic receptors in the eye, resulting in miosis (pupil constriction). This effect is a result of the opioid-induced increase in the activity of the parasympathetic nervous system, which is responsible for the constriction of the pupils.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because mydriasis (pupil dilation) is typically associated with the activation of the sympathetic nervous system, not the parasympathetic nervous system, which is stimulated in opium poisoning.
**Option B:** This option is incorrect because pin-point pupils (very small pupils) are a characteristic feature of opium poisoning, not a dilated or normal-sized pupil.
**Option C:** This option is incorrect because there is no specific correlation between pupil condition and the severity of opium poisoning.

**Clinical Pearl / High-Yield Fact**
In cases of suspected opium poisoning, it is essential to assess the pupil condition, as miosis can be a crucial diagnostic finding.

**Correct Answer: B. Pin-point pupils.**