**Core Concept**
Magnesium sulphate is a calcium channel blocker that inhibits neuromuscular transmission and has a depressant effect on the central nervous system. It is commonly used in obstetrics for eclampsia prevention and treatment, and in anesthesia for muscle relaxation.

**Why the Correct Answer is Right**
Magnesium sulphate is contraindicated in conditions where there is a risk of respiratory depression, such as severe asthma, chronic obstructive pulmonary disease (COPD), and pulmonary edema. This is because magnesium can further depress respiratory drive, leading to respiratory failure. Additionally, magnesium sulphate can also cause neuromuscular blockade, which can worsen respiratory muscle weakness in conditions like myasthenia gravis.

**Why Each Wrong Option is Incorrect**
**Option A:**
Magnesium sulphate is not contraindicated in renal failure, although caution is advised due to potential for renal magnesium overload.

**Option B:**
Magnesium sulphate is not contraindicated in cardiac arrhythmias, and may even be used to treat certain types of arrhythmias.

**Option C:**
Magnesium sulphate is not contraindicated in pregnancy-induced hypertension, and is actually used to manage severe hypertension in pregnancy.

**Clinical Pearl / High-Yield Fact**
In cases of suspected magnesium toxicity, always check serum magnesium levels and consider administering calcium gluconate to counteract the effects of magnesium.

**Correct Answer:** D.