## **Core Concept**
The question tests understanding of oxygen delivery methods and their respective concentrations. Oxygen therapy can be administered through various devices, each capable of delivering a specific range of oxygen concentrations.

## **Why the Correct Answer is Right**
A **non-rebreather mask** (option ) is capable of delivering high concentrations of oxygen, typically between 80% to 90%. This device has a one-way valve that allows the patient to exhale but prevents rebreathing of exhaled gases. It has a reservoir bag that is filled with pure oxygen, ensuring that the patient inhales a high concentration of oxygen with each breath.

## **Why Each Wrong Option is Incorrect**
* **Option A:** A nasal cannula typically delivers oxygen at a flow rate of 1-6 liters per minute (L/min), which corresponds to an oxygen concentration of approximately 24% to 44%. This is not sufficient to deliver 90% oxygen.
* **Option B:** A simple face mask can deliver oxygen concentrations ranging from 40% to 60%, depending on the flow rate. However, it does not approach the 90% oxygen delivery.
* **Option D:** A partial rebreather mask delivers oxygen concentrations between 50% to 60%. While it can provide a higher concentration than a simple face mask, it still falls short of delivering 90% oxygen.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **non-rebreather mask** is one of the devices used in acute settings to rapidly increase a patient's oxygen saturation, especially in cases of severe hypoxemia. However, its effectiveness must be monitored closely, as oxygen requirements can vary.

## **Correct Answer: C. Non-rebreather mask**