## **Core Concept**
Nerve conduction velocity varies among different types of nerve fibers. The speed of nerve conduction is primarily determined by the presence or absence of myelination and the diameter of the nerve fiber. Myelinated fibers conduct impulses faster than unmyelinated fibers due to saltatory conduction.

## **Why the Correct Answer is Right**
The slowest nerve conduction is observed in **C. Unmyelinated fibers**. This is because unmyelinated fibers lack the myelin sheath, which is crucial for saltatory conduction—a process that significantly speeds up the transmission of nerve impulses. Unmyelinated fibers, therefore, rely on continuous conduction along the entire length of the fiber, making the process slower. These fibers are typically involved in transmitting signals related to pain, temperature, and autonomic functions.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Myelinated fibers have a faster conduction velocity compared to unmyelinated fibers due to their myelin sheath, which facilitates saltatory conduction. Therefore, this option is incorrect.
- **Option B:** This option might seem plausible but is not specified; however, based on the context, if it refers to any other type of fiber that has myelination or larger diameter, it would still be faster than unmyelinated fibers.
- **Option D:** Without a specific description, it's hard to directly refute, but given that the correct answer is focused on unmyelinated fibers, any other type of nerve fiber would likely have a faster conduction velocity.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **unmyelinated fibers** are responsible for transmitting **pain** and **temperature** sensations, among other functions. These fibers are also the target for certain local anesthetics and are involved in various neuropathic pain conditions.

## **Correct Answer:** C. Unmyelinated fibers.