**Core Concept**
Ringer's Lactate (RL) solution is a type of fluid resuscitation used in critical care medicine to replace lost fluids and electrolytes. The composition of RL is designed to mimic the electrolyte composition of human plasma, with a focus on sodium, chloride, potassium, calcium, and lactate levels.

**Why the Correct Answer is Right**
The correct concentration of sodium in RL is 130 mEq/L. This is achieved through the combination of sodium chloride (0.6%) and sodium lactate (0.3%). The sodium ions are crucial for maintaining proper fluid balance, nerve function, and muscle contraction. The lactate in RL is metabolized to bicarbonate, helping to maintain acid-base balance.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not match the established composition of RL.
**Option B:** This option is incorrect because the sodium concentration in RL is not 140 mEq/L; that is more typical of normal saline.
**Option C:** This option is incorrect because the sodium concentration in RL is not 120 mEq/L; that is too low and would not be physiologically equivalent.

**Clinical Pearl / High-Yield Fact**
When administering RL, clinicians should be aware that the lactate component can lead to metabolic acidosis if excessive amounts are administered or if the patient's liver is unable to metabolize lactate adequately.

**Correct Answer: C. 130 mEq/L**