**Core Concept**
The question tests the understanding of the transport of dissolved oxygen in plasma under hyperbaric conditions. The Bohr effect and the role of oxygen-carrying capacity of hemoglobin are crucial in this context.

**Why the Correct Answer is Right**
At 4 ATA, the partial pressure of oxygen (pO2) in arterial blood is significantly increased. However, the amount of dissolved oxygen in plasma is relatively small compared to the oxygen bound to hemoglobin. The correct answer is based on the concept that the increase in pO2 at high pressure does not significantly increase the amount of dissolved oxygen in plasma. The oxygen-carrying capacity of hemoglobin is much higher than the oxygen dissolved in plasma, and most of the oxygen is transported bound to hemoglobin.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it doesn't take into account the small amount of oxygen dissolved in plasma compared to the oxygen bound to hemoglobin.

**Option B:** This option is incorrect because it overestimates the effect of high pressure on the amount of dissolved oxygen in plasma.

**Option C:** This option is incorrect because it doesn't provide a specific value for the amount of dissolved oxygen in plasma.

**Clinical Pearl / High-Yield Fact**
Under hyperbaric conditions, the oxygen-carrying capacity of hemoglobin is increased, but the amount of dissolved oxygen in plasma remains relatively small. This is an important consideration in the treatment of carbon monoxide poisoning and other conditions where hyperbaric oxygen therapy is used.

**Correct Answer:** B. 1.5 ml