**Core Concept**
Barium carbonate poisoning involves the ingestion of a toxic compound that can cause severe symptoms due to its chemical properties. Barium carbonate is a highly soluble compound that can release barium ions, leading to a range of systemic effects.

**Why the Correct Answer is Right**
Barium ions interfere with the binding of potassium ions to the Na+/K+-ATPase pump in the cell membrane, disrupting the normal functioning of this enzyme. This leads to an increase in intracellular sodium and a decrease in intracellular potassium, causing cellular depolarization and ultimately, cardiac arrhythmias and muscle weakness. The barium ions also stimulate the parasympathetic nervous system, leading to bradycardia and vasodilation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not describe the primary mechanism of barium carbonate poisoning.
**Option B:** While barium carbonate can cause gastrointestinal symptoms, such as nausea and vomiting, this is not the primary effect of barium carbonate poisoning.
**Option C:** This option is incorrect as barium carbonate does not primarily cause renal failure or acute kidney injury.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that barium carbonate poisoning can cause severe cardiac arrhythmias and muscle weakness due to its effects on the Na+/K+-ATPase pump.

**Correct Answer: B. Gastrointestinal symptoms are the primary presentation of barium carbonate poisoning.**