**Core Concept**
The underlying principle being tested is the effect of barium carbonate poisoning on the body's electrolyte balance, particularly its impact on potassium levels. Barium is a **potassium channel blocker**, and its ingestion can lead to **hypokalemia**.

**Why the Correct Answer is Right**
Barium carbonate poisoning can cause **hypokalemia** due to its effect on potassium channels, leading to an inability of the cells to maintain a normal potassium balance. This results in generalized muscle weakness, as potassium is crucial for muscle function and **neuromuscular transmission**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be incorrect as the primary issue is not directly related to this electrolyte in the context of barium poisoning.
**Option B:** Similarly, this option does not directly correlate with the primary effect of barium carbonate ingestion.
**Option D:** This option is also incorrect as the primary electrolyte imbalance caused by barium carbonate is not related to this choice.

**Clinical Pearl / High-Yield Fact**
In cases of barium poisoning, it's crucial to monitor and manage **potassium levels** closely, as **hypokalemia** can lead to severe muscle weakness and potentially life-threatening cardiac arrhythmias.

**Correct Answer:** D. Hypokalemia