**Core Concept**
The velocity of conduction in the heart is influenced by the type of cardiac tissue and its function. The **Purkinje fibers** are specialized conducting fibers responsible for rapidly spreading the impulse of contraction through the ventricles.

**Why the Correct Answer is Right**
The correct answer choice reflects the fastest conduction velocity, which is a characteristic of **Purkinje fibers**. This rapid conduction is crucial for synchronized ventricular contraction, ensuring efficient pumping of blood. The velocity is facilitated by the large diameter of these fibers and their high concentration of **gap junctions**, which enable rapid electrical transmission between cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not represent the fastest conduction velocity.
**Option B:** Similarly, this option is too slow for the conduction velocity of Purkinje fibers.
**Option D:** This is also incorrect as it underestimates the conduction speed of Purkinje fibers.

**Clinical Pearl / High-Yield Fact**
The **Purkinje fibers** play a critical role in the heart's electrical conduction system, and their dysfunction can lead to severe cardiac arrhythmias. Understanding their conduction velocity is essential for diagnosing and managing cardiac rhythm disorders.

**Correct Answer:** Correct Answer: C. 2-4 m/s.