**Core Concept**
Central neuraxial blockade involves the injection of local anesthetics or other agents into the cerebrospinal fluid (CSF) surrounding the spinal cord, which can selectively block nerve impulses. This blockade can be differential, meaning it affects some nerve fibers more than others, depending on the specific properties of the agent used.

**Why the Correct Answer is Right**
The differential blockade achieved by central neuraxial blockade is primarily due to the varying sensitivity of nerve fibers to local anesthetics. Small, unmyelinated fibers (C fibers) responsible for transmitting pain and temperature are more susceptible to blockade than larger, myelinated fibers (A fibers) responsible for transmitting touch and proprioception. This is because local anesthetics preferentially bind to and block sodium channels on small nerve fibers, which are more densely packed and have a higher concentration of sodium channels.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect, as this option does not describe the mechanism of differential blockade in central neuraxial blockade.
* **Option B:** Incorrect, as this option is unrelated to the differential blockade achieved by central neuraxial blockade.
* **Option C:** Incorrect, as this option does not accurately describe the properties of nerve fibers that contribute to differential blockade in central neuraxial blockade.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the differential blockade achieved by central neuraxial blockade can result in a relative preservation of motor function, making it a useful technique for surgeries and procedures where motor weakness is undesirable.

**Correct Answer: C. Varying sensitivity of nerve fibers to local anesthetics.**