**Core Concept**
Ringer lactate solution, also known as lactated Ringer's solution, is a type of intravenous fluid used to treat shock, dehydration, and other conditions. It contains a balanced mixture of electrolytes, including sodium, chloride, potassium, calcium, and lactate.

**Why the Correct Answer is Right**
Ringer lactate solution contains a relatively low concentration of potassium ions (K+). The typical composition of Ringer lactate solution is: sodium chloride (6 g/L), sodium lactate (3 g/L), calcium chloride (0.2 g/L), and potassium chloride (0.3 g/L). The low concentration of potassium is intended to prevent hyperkalemia, a potentially life-threatening condition characterized by elevated potassium levels in the blood.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Ringer lactate solution is not designed to be a high-potassium solution. Its composition is carefully balanced to provide essential electrolytes without causing hyperkalemia.
**Option B:** This option is incorrect because the actual concentration of potassium in Ringer lactate solution is lower than that found in many other types of intravenous fluids.

**Clinical Pearl / High-Yield Fact**
When administering Ringer lactate solution, it's essential to monitor potassium levels closely, especially in patients with pre-existing kidney disease or other conditions that may affect potassium balance.

**Correct Answer: D. 3 mEq/L**