**Core Concept**
The Ellis classification is used to describe fractures or cracks in teeth, focusing on the extent of tooth structure involvement. **Tooth fractures** can range from minor enamel damage to more severe exposures of the dental pulp.

**Why the Correct Answer is Right**
An Ellis class IV fracture involves the enamel, dentin, and exposes the **pulpal tissue**. This is the most severe form of tooth fracture in the Ellis classification, as it compromises the vitality of the tooth by directly exposing the **pulp**.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify exposure of the pulp.
**Option B:** Incorrect as it refers to a less severe form of fracture.
**Option C:** Incorrect because it does not involve exposure of the pulp.

**Clinical Pearl / High-Yield Fact**
In clinical practice, an Ellis class IV fracture is a dental emergency requiring immediate attention to relieve pain and prevent infection, often necessitating **root canal therapy**.

**Correct Answer:** D. Involves enamel, dentin, and exposes the pulp.