**Core Concept**
The question tests the student's understanding of ion channels, which are crucial for the control of electrical excitability in cells, including neurons and cardiac myocytes. Ion channels are proteins that form pores in the cell membrane, allowing specific ions to pass through and regulate the electrical properties of cells.

**Why the Correct Answer is Right**
Ion channels are proteins that form pores in the cell membrane, allowing specific ions to pass through. In contrast to pumps, which actively transport ions against their concentration gradient, ion channels are passive, allowing ions to flow down their concentration gradient. The correct answer, **K+ channels**, are a type of voltage-gated ion channel that controls the flow of potassium ions (K+) into or out of cells.

**Why Each Wrong Option is Incorrect**
* **Option A:** Pumps (e.g., Na+/K+ ATPase) actively transport ions against their concentration gradient, using energy from ATP hydrolysis.
* **Option B:** Receptors (e.g., nicotinic acetylcholine receptors) are proteins that bind to specific ligands, triggering a response in the cell, but they are not ion channels.
* **Option D:** Gated Ca2+ channels are a type of ion channel, but they are not the correct answer in this case, as the question is asking for a specific example of an ion channel.

**Clinical Pearl / High-Yield Fact**
Ion channels are crucial for the control of electrical excitability in cells, and dysfunction of ion channels is associated with various diseases, including epilepsy, cardiac arrhythmias, and myotonia congenita.

**Correct Answer:** C.