**Core Concept**
The anesthesia machine's pressure system consists of various components that regulate and monitor gas flow, pressure, and vaporization. Understanding the correct arrangement of these components is essential for ensuring safe and effective anesthesia delivery.

**Why the Correct Answer is Right**
The correct arrangement of components from lowest to highest pressure is as follows:
- **Flow indicators** (iii) typically measure the flow of gases in liters per minute (L/min) and are usually the lowest-pressure component.
- **Vaporizer mounting devices** (i) are located after the flow meters and regulate the concentration of anesthetic vapor in the gas mixture.
- **Pipeline pressure gauge** (iv) measures the pressure of the pipeline gas supply, which is usually higher than the flow meters and vaporizers.
- **Hanger yoke assembly** (ii) is connected to the common gas outlet and is the highest-pressure component, as it delivers the gas mixture to the patient.

**Why Each Wrong Option is Incorrect**
**Option A:** The correct arrangement is not (iii), (i), (iv), (ii) as it places the flow indicators before the vaporizer mounting devices.
**Option B:** The correct arrangement is not (i), (iv), (iii), (ii) as it places the pipeline pressure gauge before the flow indicators.
**Option C:** The correct arrangement is not (ii), (i), (iii), (iv) as it places the hanger yoke assembly before the vaporizer mounting devices.
**Option D:** The correct arrangement is not (iii), (iv), (ii), (i) as it places the pipeline pressure gauge before the hanger yoke assembly.

**Clinical Pearl / High-Yield Fact**
When checking the anesthesia machine, it's essential to verify that the flow indicators are functioning correctly, the vaporizer is set to the correct concentration, and the pipeline pressure gauge is within the safe range.

**✓ Correct Answer: A. (iii), (i), (iv), (ii)**