**Core Concept**
Hyperbaric oxygenation is a medical treatment where a patient breathes pure oxygen in a pressurized room or through a tube. This treatment is used for various conditions, including carbon monoxide poisoning, gas gangrene, and decompression sickness. The pressure of oxygen is carefully controlled to prevent lung damage.

**Why the Correct Answer is Right**
The maximum allowed pressure of oxygen in hyperbaric oxygenation is 3 atmospheres absolute (ATA). This is because breathing pure oxygen at pressures above 3 ATA can cause oxygen toxicity, leading to convulsions, lung damage, and even death. The 3 ATA limit helps to minimize the risk of oxygen toxicity while still providing therapeutic benefits.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide any information about the maximum allowed pressure of oxygen in hyperbaric oxygenation.
**Option B:** This option is incorrect because it is a lower pressure than 3 ATA, which would not be sufficient for therapeutic benefits.
**Option C:** This option is incorrect because it is a much higher pressure than 3 ATA, which would increase the risk of oxygen toxicity.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that hyperbaric oxygenation is not a substitute for standard medical treatment. The treatment should only be administered under the guidance of a qualified medical professional.

**Correct Answer: B. 2 ATA**