**Core Concept**
Preoxygenation is a critical step in anesthesia and emergency medicine aimed at increasing the body's oxygen stores before a procedure or critical event. The goal is to delay the onset of significant desaturation during apnea or hyperventilation.

**Why the Correct Answer is Right**
The ideal time for preoxygenation is typically 3-5 minutes, during which the patient is asked to breathe 100% oxygen through a mask. This allows for the following:

* The patient's functional residual capacity (FRC) of oxygen is replenished and maximized.
* The oxygen stores in the blood, muscles, and fatty tissues are increased, delaying the onset of desaturation.
* The Bohr effect is minimized, allowing hemoglobin to maintain its oxygen-carrying capacity for a longer period.

**Why Each Wrong Option is Incorrect**
**Option A:** 1 minute is too short to effectively replenish the patient's oxygen stores.
**Option B:** 10 minutes is excessive and may not be practical in all clinical situations.
**Option C:** 15 minutes is not supported by current evidence and may lead to unnecessary delay.

**Clinical Pearl / High-Yield Fact**
The "4-minute rule" is a useful mnemonic to remember the ideal preoxygenation time: "4 minutes to fill, 4 minutes to spare, and 4 minutes to wait before apnea."

**Correct Answer: C. 5 minutes**