**Core Concept**
Normal intrapleural pressure is a crucial aspect of respiratory physiology, maintaining the balance between lung inflation and deflation. It is a slightly negative pressure, generated by the elastic recoil of the lungs and the surface tension of the pleural fluid, which helps to keep the lungs expanded and facilitate gas exchange.

**Why the Correct Answer is Right**
The correct answer is due to the delicate balance between the elastic recoil of the lungs and the surface tension of the pleural fluid. The lungs tend to collapse due to their elastic recoil, but the negative intrapleural pressure helps to counteract this force and maintain lung expansion. Additionally, the intrapleural pressure is influenced by the pressure exerted by the diaphragm and the intercostal muscles during inspiration, which helps to increase the negative pressure and facilitate lung inflation.

**Why Each Wrong Option is Incorrect**
**Option A:** This answer is incorrect because it does not accurately reflect the normal physiological state of intrapleural pressure. A positive pressure would lead to lung collapse.
**Option B:** This answer is incorrect because it is not a commonly accepted measurement of intrapleural pressure. The normal range is typically around -4 to -6 cmH2O.
**Option C:** This answer is incorrect because it is not a precise measurement of intrapleural pressure. The normal range is typically around -4 to -6 cmH2O.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the intrapleural pressure is influenced by the surface tension of the pleural fluid, which is decreased by the presence of surfactant. Surfactant is a critical component of lung function, and its deficiency can lead to respiratory distress syndrome in premature infants.

**Correct Answer: A. -4 to -6 cmH2O**