**Core Concept**
Organophosphate poisoning is a medical emergency caused by the inhibition of acetylcholinesterase, leading to an accumulation of acetylcholine in the synaptic cleft. This results in overstimulation of muscarinic and nicotinic receptors, manifesting as various systemic symptoms.

**Why the Correct Answer is Right**
The patient's symptoms, including pinpoint pupils, salivation, lacrimation, tremors, and red tears, are characteristic of organophosphate poisoning. The inhibition of acetylcholinesterase leads to an accumulation of acetylcholine, which stimulates muscarinic receptors in the eye, causing miosis (pinpoint pupils), and nicotinic receptors in the salivary and lacrimal glands, resulting in excessive salivation and lacrimation. The tremors are likely due to nicotinic receptor stimulation in the neuromuscular junction. The low plasma cholinesterase level (30% of normal) confirms the diagnosis of organophosphate poisoning.

**Why Each Wrong Option is Incorrect**
**Option B:** Datura poisoning is caused by anticholinergic toxins, which inhibit the action of acetylcholine at muscarinic receptors, leading to symptoms such as mydriasis (dilated pupils), dry mouth, and confusion. This is the opposite of what is seen in organophosphate poisoning.
**Option C:** Opioid poisoning primarily causes central nervous system depression, leading to symptoms such as respiratory depression, sedation, and miosis. While opioids can cause pinpoint pupils, they do not cause the other symptoms seen in organophosphate poisoning.
**Option D:** Pontine hemorrhage is a catastrophic condition that can cause pinpoint pupils due to damage to the pons, but it does not cause the other symptoms seen in organophosphate poisoning, such as excessive salivation and lacrimation.

**Clinical Pearl / High-Yield Fact**
In cases of suspected organophosphate poisoning, atropine and pralidoxime are the mainstay treatments. Atropine is an anticholinergic agent that counteracts the muscarinic effects of excess acetylcholine, while pralidoxime reactivates acetylcholinesterase.

**✓ Correct Answer: A. Organophosphate poisoning**