Which solution contains lactate, potassium, and calcium?

• A. Normal saline.
• B. Dextrose 5% in water.
• C. Lactated Ringer's.
• D. Hypertonic saline.

Answer: (C)

Fluid composition is what this question tests. Lactated Ringer's contains a balanced mix of electrolytes—sodium, chloride, potassium, and calcium—along with lactate, which acts as a buffer that the body can convert to bicarbonate to help maintain acid-base balance. This combination makes it the solution that provides lactate, potassium, and calcium all in one.

Normal saline offers only sodium and chloride, with no lactate, potassium, or calcium. Dextrose 5% in water supplies glucose and, after the glucose is used, essentially becomes free water with little or no electrolytes. Hypertonic saline has a high sodium chloride content but does not include lactate, potassium, or calcium.