Okay, let's tackle this question. The user is asking about the partial pressure of oxygen at 760 mmHg atmospheric pressure. Hmm, I remember that atmospheric pressure is the total pressure of all gases in the air. At sea level, it's 760 mmHg. But the partial pressure of a specific gas depends on its concentration in the air.

Wait, the question is probably about the partial pressure of oxygen (O2) in the atmosphere. The normal composition of air is about 21% oxygen. So, if the total atmospheric pressure is 760 mmHg, then the partial pressure of oxygen would be 21% of that. Let me calculate that: 760 mmHg * 0.21 = 159.6 mmHg. So approximately 160 mmHg.

But wait, the options weren't provided here. The user didn't list the options. Hmm, maybe the original question had options like 160, 760, 100, etc. The correct answer would be 160 mmHg. The user's correct answer is missing the options, but the assistant needs to explain the concept regardless.

So the core concept here is the calculation of partial pressure using the ideal gas law, which states that partial pressure = total pressure * mole fraction. For oxygen, which is 21% in air, it's 0.21 * 760. That's the main point.

Now, the wrong options might include the total atmospheric pressure (760 mmHg), which is incorrect because that's the sum of all gas pressures. Another wrong answer could be the partial pressure of nitrogen, which is about 760 * 0.78 = 592.8 mmHg. Or maybe the partial pressure of oxygen in alveoli, which is lower due to CO2 and water vapor. The alveolar oxygen partial pressure is around 100 mmHg, but that's after gas exchange. So if someone confuses atmospheric with alveolar, that's a mistake.

The clinical pearl here is to remember that the partial pressure of oxygen in atmospheric air is about 160 mmHg, but in the alveoli, it drops to around 100 mmHg. Also, water vapor pressure (47 mmHg) and CO2 affect alveolar values. So the key is distinguishing between atmospheric and alveolar partial pressures.

Putting it all together, the explanation should cover the calculation method, the correct partial pressure, why other values are wrong, and the clinical distinction between atmospheric and alveolar pressures.

**Core Concept**
The partial pressure of a gas in a mixture is calculated by multiplying the total pressure by the gas's volume fraction. For atmospheric oxygen (21% of air), this is **0.21 × 760 mmHg = 159.6 mmHg ≈ 160 mmHg**.

**Why the Correct Answer is Right**
At sea level, atmospheric pressure is 760 mmHg. Dry air contains ~21% oxygen. Using Dalton’s Law, the partial pressure of oxygen (PO₂) = 0.21 × 760 =

✓ Correct Answer: B. 160