**Core Concept**
Central Chemoreceptors are specialized neurons in the medulla oblongata that detect changes in the chemical composition of the cerebrospinal fluid (CSF) to regulate breathing. They are sensitive to the levels of carbon dioxide (CO2) and pH in the CSF, which is in close equilibrium with the partial pressure of CO2 in arterial blood.

**Why the Correct Answer is Right**
The correct answer is related to the fact that central chemoreceptors are more sensitive to changes in the hydrogen ion concentration (pH) of the CSF than to changes in the partial pressure of CO2 (pCO2). This is because the pH of the CSF is more directly affected by the buffering capacity of bicarbonate ions, which is influenced by the partial pressure of CO2. As CO2 diffuses into the CSF, it reacts with water to form carbonic acid, which then dissociates into hydrogen ions and bicarbonate ions. This increase in hydrogen ions reduces the pH of the CSF, stimulating the central chemoreceptors to increase ventilation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the sensitivity of central chemoreceptors.
* **Option B:** Central chemoreceptors are not primarily sensitive to changes in oxygen levels.
* **Option C:** While peripheral chemoreceptors are sensitive to changes in oxygen levels, central chemoreceptors are not.

**Clinical Pearl / High-Yield Fact**
The central chemoreceptors are insensitive to changes in the partial pressure of oxygen (pO2) in arterial blood, and their primary function is to regulate ventilation in response to changes in CO2 levels and pH in the CSF.

**Correct Answer: D. pH in CSF**