**Core Concept**
The patient's presentation is consistent with an excessive cholinergic activity, which is a hallmark of organophosphate poisoning. This is due to the inhibition of acetylcholinesterase, the enzyme responsible for breaking down acetylcholine, leading to an accumulation of acetylcholine in the synapses.

**Why the Correct Answer is Right**
The patient's symptoms, including pinpoint pupils (miosis), excessive salivation (hypersalivation), lacrimation, tremors, and red tears, are all characteristic of organophosphate poisoning. This is because organophosphates irreversibly inhibit acetylcholinesterase, leading to an accumulation of acetylcholine in the neuromuscular junctions, causing overstimulation of nicotinic and muscarinic receptors. The decreased plasma cholinesterase level (30% of normal) further supports this diagnosis, as it indicates the presence of an organophosphate compound that has inhibited the enzyme.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so we cannot comment on it.
* **Option B:** This option is not provided, so we cannot comment on it.
* **Option C:** This option is not provided, so we cannot comment on it.
* **Option D:** This option is not provided, so we cannot comment on it.

**Clinical Pearl / High-Yield Fact**
The diagnosis of organophosphate poisoning can be challenging, but the presence of pinpoint pupils, excessive salivation, and a decreased plasma cholinesterase level should raise suspicion. It is essential to consider the patient's occupation, exposure history, and any recent pesticide use.

**Correct Answer:** B. Organophosphate poisoning.