**Core Concept**
Belladonna poisoning occurs due to the ingestion of atropine-rich plant extracts, leading to anticholinergic toxicity. The primary mechanism involves the blockade of muscarinic acetylcholine receptors, resulting in symptoms such as tachycardia, dry mouth, blurred vision, and delirium.

**Why the Correct Answer is Right**
Physostigmine is a reversible cholinesterase inhibitor, which can effectively counteract the anticholinergic effects of atropine by increasing the concentration of acetylcholine in the synaptic cleft. This can help to restore normal muscarinic receptor activity and alleviate symptoms of belladonna poisoning. The ability of physostigmine to cross the blood-brain barrier makes it an effective antidote for central as well as peripheral anticholinergic toxicity.

**Why Each Wrong Option is Incorrect**
**Option A:** Atropine itself is the primary toxin responsible for belladonna poisoning and would exacerbate symptoms if administered as an antidote.
**Option B:** Activated charcoal may be used to prevent further absorption of atropine, but it does not address the already established anticholinergic effects.
**Option C:** Naloxone is an opioid antagonist and has no role in the management of belladonna poisoning.

**Clinical Pearl / High-Yield Fact**
Physostigmine is a unique antidote that can cross the blood-brain barrier, making it effective for treating central anticholinergic toxicity, whereas other anticholinergic antagonists like benztropine are primarily used for peripheral effects.

**Correct Answer: C. Physostigmine**