**Core Concept**
The conduction velocity of impulses through the heart is influenced by the properties of the cardiac tissue, such as the density of gap junctions and the presence of ion channels. An increase in conduction velocity is crucial for maintaining a coordinated heartbeat and preventing arrhythmias.

**Why the Correct Answer is Right**
The correct answer is **C. Hyperkalemia**. Hyperkalemia increases the conduction velocity of impulses through the heart by increasing the density of gap junctions between cardiac myocytes. This allows for faster propagation of electrical signals, which can lead to a faster heart rate. The mechanism behind this is the selective increase in the expression of connexin 43, a key component of gap junctions. Additionally, hyperkalemia can also increase the activity of certain ion channels, such as the sodium-potassium pump, which contributes to the increased conduction velocity.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hypokalemia actually decreases conduction velocity by reducing the density of gap junctions and altering the activity of ion channels.
* **Option B:** Acidosis can decrease conduction velocity by reducing the activity of ion channels and the density of gap junctions.
* **Option D:** Hypothermia decreases conduction velocity by reducing the activity of ion channels and the density of gap junctions.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that hyperkalemia can have both beneficial and detrimental effects on cardiac conduction velocity, depending on the context. In the setting of a cardiac arrest, hyperkalemia can increase conduction velocity, potentially leading to a return of spontaneous circulation. However, in the setting of a normal heart, hyperkalemia can lead to arrhythmias and decreased cardiac function.

**Correct Answer:** C. Hyperkalemia increases conduction velocity of impulses through heart.