**Core Concept**
Eclampsia is a severe complication of preeclampsia, characterized by new-onset seizures in a pregnant woman. The primary goal of treatment is to prevent further seizures and ensure maternal and fetal safety.

**Why the Correct Answer is Right**
Magnesium sulfate is the treatment of choice for eclampsia due to its rapid onset of action, effectiveness in seizure prophylaxis, and safety profile for both mother and fetus. It works by inhibiting neuronal activity and stabilizing neuronal membranes, reducing the frequency and severity of seizures.

**Why Each Wrong Option is Incorrect**
**Option A:** Phenobarbital is not the first-line treatment for eclampsia, although it may be used in certain cases where magnesium sulfate is contraindicated or ineffective.
**Option B:** Diazepam is not typically used in the treatment of eclampsia due to its slower onset of action and potential for respiratory depression in both mother and fetus.
**Option C:** Lorazepam is not the preferred choice for eclampsia treatment, as it can cause respiratory depression and has a slower onset of action compared to magnesium sulfate.

**Clinical Pearl / High-Yield Fact**
Magnesium sulfate is the only medication approved by the FDA for the treatment of eclampsia, and it is crucial to monitor maternal and fetal vital signs closely during administration to avoid complications.

**Correct Answer:** C. Magnesium sulfate.