**Core Concept**
Excitatory postsynaptic potentials (EPSPs) are a type of postsynaptic potential that occurs in neurons, resulting from the activation of ligand-gated ion channels by neurotransmitters. This leads to an influx of positively charged ions, such as sodium and calcium, into the postsynaptic neuron, causing depolarization.

**Why the Correct Answer is Right**
EPSPs are generated when neurotransmitters bind to their respective receptors on the postsynaptic neuron, causing the opening of ligand-gated ion channels. The most common type of ligand-gated ion channel involved in EPSPs is the nicotinic acetylcholine receptor. When acetylcholine binds to this receptor, it allows sodium ions to flow into the postsynaptic neuron, resulting in depolarization. This depolarization can then trigger an action potential if the threshold is reached.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because it does not specify the type of postsynaptic potential.
* **Option B:** Incorrect because it is too broad, as there are many types of postsynaptic potentials, not just EPSPs.
* **Option C:** Incorrect because it is a type of postsynaptic potential that occurs in the absence of neurotransmitter release, not a type of EPSP.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that EPSPs can be either excitatory or inhibitory, depending on the type of neurotransmitter and receptor involved. For example, glycine and GABA are inhibitory neurotransmitters that can cause inhibitory postsynaptic potentials (IPSPs), whereas glutamate and aspartate are excitatory neurotransmitters that can cause EPSPs.

**Correct Answer:** D. Excitatory postsynaptic potential.