**Core Concept**
The question is testing the properties of volatile anaesthetic agents, specifically their boiling points. Volatile anaesthetics are commonly used in inhalational anaesthesia and have distinct properties that affect their use in clinical settings.

**Why the Correct Answer is Right**
The correct answer is based on the boiling point of the anaesthetic agent. The boiling point is an important property of volatile anaesthetics as it affects their vapour pressure and solubility in blood. Agents with a boiling point greater than 75°C tend to have a higher vapour pressure, making them more potent and potentially more toxic. This is because they require less energy to vaporize, resulting in a higher concentration of vapour at a given temperature.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option is incorrect because it does not specify the boiling point of the agent. Without this information, it is impossible to determine its relative potency or solubility.
* **Option B:** This option is incorrect because it suggests a boiling point less than 75°C, which would imply a lower vapour pressure and potentially lower potency.
* **Option C:** This option is incorrect because it implies a boiling point close to 75°C, which is not significantly different from the threshold. This would not provide a clear indication of the agent's potency or solubility.

**Clinical Pearl / High-Yield Fact**
When selecting a volatile anaesthetic agent, it is essential to consider its boiling point as it affects its vapour pressure, solubility in blood, and overall potency. Agents with boiling points greater than 75°C tend to be more potent and potentially more toxic, requiring careful monitoring and dosing.

**Correct Answer: C. Ethrane (Enflurane) - Enflurane has a boiling point of 56.5°C, the other option is Sevoflurane which has a boiling point of 58.5°C, but the closest option to >75°C would be Sevoflurane**