**Core Concept**
The question pertains to the legal definition of grievous hurt as per the Indian Penal Code (IPC). Grievous hurt is a term used in the context of criminal law to describe severe injuries that can have long-term consequences for the victim.

**Why the Correct Answer is Right**
Grievous hurt is defined in Section 320 of the IPC, which lists various types of injuries that are considered grievous. These include permanent privation of the sight of either eye, permanent privation of the hearing of either ear, and any hurt which endangers life or which causes the sufferer to be during the space of twenty days in severe bodily pain, or unable to follow his ordinary pursuits. The IPC categorizes these injuries to ensure that those responsible for causing them are held accountable for their actions.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because Section 319 of the IPC defines hurt, whereas Section 320 specifically defines grievous hurt.
* **Option B:** This is incorrect because Section 326 of the IPC deals with voluntarily causing grievous hurt by dangerous weapons or means, but it does not define grievous hurt.
* **Option C:** This is incorrect because Section 299 of the IPC defines culpable homicide, which is a separate legal concept from grievous hurt.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the IPC categorizes various types of injuries to ensure that those responsible for causing them are held accountable for their actions. Understanding the nuances of these definitions can help medical professionals provide accurate testimony in court cases.

**Correct Answer: D. Section 320 of the IPC.**