**Core Concept**
Hyponatremia, specifically symptomatic or severe hyponatremia, requires prompt and appropriate management to prevent complications such as seizures and brain herniation. In this scenario, the patient is asymptomatic, but the serum sodium level is low, necessitating careful evaluation and management.

**Why the Correct Answer is Right**
The patient's serum sodium level is 120 meq/L, which is considered hyponatremic. In the absence of symptoms, the primary aim is to identify and treat the underlying cause of hyponatremia. The first step is to assess the patient's volume status, as hypovolemic hyponatremia can be managed differently than euvolemic or hypervolemic hyponatremia. In this case, the patient is asymptomatic, suggesting that the hyponatremia may be euvolemic or hypervolemic in nature.

**Why Each Wrong Option is Incorrect**
**Option A:** Administering hypertonic saline without identifying the underlying cause of hyponatremia is inappropriate, as it may worsen volume overload or hypertension.
**Option B:** Restricting fluids is not the primary management strategy for asymptomatic hyponatremia, as the goal is to identify and treat the underlying cause rather than simply correcting the serum sodium level.
**Option C:** Diuretics may be used in the management of hyponatremia, but not without first assessing the patient's volume status and identifying the underlying cause.

**Clinical Pearl / High-Yield Fact**
In patients with hyponatremia, it's essential to differentiate between hypovolemic, euvolemic, and hypervolemic states, as the underlying cause and management strategy vary depending on the volume status.

**Correct Answer: C.**