**Core Concept**
Minimum alveolar concentration (MAC) is a measure of anesthetic potency, defined as the concentration of an inhaled anesthetic in the lungs that is required to prevent movement in 50% of subjects in response to a painful stimulus, such as a surgical incision. It is an important parameter in anesthesiology for selecting the appropriate anesthetic agent.

**Why the Correct Answer is Right**
MAC values are used to compare the potency of different anesthetic agents. A lower MAC value indicates a more potent anesthetic. The MAC of a mixture of anesthetics is the MAC of the most potent anesthetic in the mixture. For example, the MAC of a mixture of nitrous oxide (MAC = 104%) and halothane (MAC = 0.75%) is the MAC of halothane (0.75%). This is because halothane is the most potent anesthetic in the mixture.

**Why Each Wrong Option is Incorrect**
* **Option A:** This statement may be true, but it requires more information to determine its accuracy. For example, the MAC of a mixture of two anesthetics depends on their potency and the partial pressures of each anesthetic in the lungs.
* **Option B:** This statement is incorrect because the MAC of a mixture of anesthetics is the MAC of the most potent anesthetic in the mixture, not the MAC of the least potent anesthetic.
* **Option C:** This statement is incorrect because the MAC of a mixture of anesthetics is not the MAC of the anesthetic with the highest partial pressure in the lungs.

**Clinical Pearl / High-Yield Fact**
When selecting an anesthetic agent, anesthesiologists should consider the MAC value to determine the required concentration of the agent to achieve the desired level of anesthesia. A lower MAC value indicates a more potent anesthetic, which may require less anesthetic gas to achieve the same level of anesthesia.

**Correct Answer:** B. This statement is incorrect because the MAC of a mixture of anesthetics is the MAC of the most potent anesthetic in the mixture, not the MAC of the least potent anesthetic.