Okay, let's tackle this question step by step. The question is about why 100% oxygen is administered after discontinuing nitrous oxide and removing the endotracheal tube.

First, I need to recall the core concept here. Nitrous oxide is a commonly used anesthetic gas. When it's discontinued, there's a rapid elimination from the body. But there's a specific reason why oxygen is given afterward.

The core concept might be related to diffusion hypoxia. Diffusion hypoxia occurs when a high concentration of a volatile anesthetic (like nitrous oxide) is discontinued, leading to a situation where the alveolar concentration of the anesthetic is higher than the inspired concentration. This creates a gradient that causes the anesthetic to diffuse into the bloodstream, potentially displacing oxygen and leading to hypoxia. Administering 100% oxygen after stopping nitrous oxide helps to flush out any residual anesthetic from the alveoli, preventing this hypoxia.

Now, looking at the correct answer options. The question is asking what 100% oxygen is administered to prevent. The answer is likely diffusion hypoxia. So the correct answer would be that oxygen is given to prevent diffusion hypoxia caused by residual nitrous oxide.

For the wrong options, they might include things like malignant hyperthermia, airway obstruction, or postoperative nausea. Malignant hyperthermia is a genetic condition triggered by certain anesthetics, but it's not related to nitrous oxide specifically. Airway obstruction is a separate issue, and postoperative nausea is more related to other factors like opioid use or volatile anesthetics.

The clinical pearl here is that diffusion hypoxia is a key concept in anesthesia. Remembering that nitrous oxide's rapid elimination can lead to a concentration gradient that displaces oxygen, hence the need for 100% oxygen post-anesthesia. This is a high-yield point for exams like NEET PG or USMLE.

I need to structure the explanation with the required sections: Core Concept, Why Correct is Right, Why Wrong are Wrong, Clinical Pearl, and Correct Answer. Make sure to use bold labels and keep each section concise. Also, check the character count to stay within limits. Let me put this all together now.

**Core Concept**
The administration of 100% oxygen after discontinuation of nitrous oxide prevents **diffusion hypoxia**. Nitrous oxide diffuses rapidly from the blood into the alveoli post-discontinuation, displacing oxygen and reducing alveolar O₂ tension. This creates a gradient that drives O₂ from the blood into the alveoli, risking hypoxemia.

**Why the Correct Answer is Right**
100% oxygen increases alveolar O₂ concentration, counteracting nitrous oxide’s displacement of oxygen. This prevents **diffusion hypoxia** by maintaining a high alveolar-to-arterial O₂ gradient, ensuring oxygen diffuses into the blood rather than being lost. Nitrous oxide’s rapid elimination (half-life ~10 minutes) makes this intervention critical during emergence from anesthesia.

**Why Each Wrong Option is Incorrect**
**Option A:** Malignant hyperthermia is a genetic disorder triggered by volatile anesthetics or succinylcholine, not nitrous oxide.
**Option B:** Airway

✓ Correct Answer: A. Diffusion Hypoxia