**Core Concept**
The oleander plant is a toxic plant known to cause cardiac arrest and arrhythmias due to its active principle, which acts as a potassium channel blocker in the heart.

**Why the Correct Answer is Right**
The active principle of oleander, known as neriine glycosides, specifically digitoxin and digoxin, act by inhibiting the sodium-potassium pump, leading to an increase in intracellular sodium and a decrease in intracellular potassium, thereby increasing the likelihood of arrhythmias. This inhibition disrupts the normal functioning of the cardiac cell membrane, leading to hyperkalemia, bradycardia, and potentially, cardiac arrest.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because oleander does not contain tropane alkaloids, which are found in plants like Atropa belladonna.
**Option B:** This is incorrect because aconitine is the active principle of Aconitum, a different toxic plant, which acts by blocking sodium channels.
**Option C:** This is incorrect because taxine is the active principle of Taxus, another toxic plant, which acts by inhibiting the cardiac sodium-potassium pump but through a different mechanism.

**Clinical Pearl / High-Yield Fact**
Remember that oleander toxicity can lead to a characteristic electrocardiogram (ECG) pattern, known as "digitalis effect," characterized by a prolonged PR interval, widened QRS complex, and eventually, ventricular fibrillation.

**Correct Answer: A. Neriine glycosides**