Which of the following components is primarily contained in Dextrose 5% in water (D5W)?

Dextrose 5% in water (D5W) primarily contains free water, as it is essentially a sugar solution where dextrose is dissolved in water. The composition of D5W indicates that it serves as a source of fluid and carbohydrates.

When administered, D5W provides a significant volume of water to the patient. This can be particularly beneficial for hydration purposes and is often used in clinical settings to restore fluid balance. While it also supplies a small amount of calories and can be metabolized for energy, its main feature is the free water it provides.

In contrast to the other options, D5W does not contain high sodium or potassium concentrations, nor does it serve as an electrolyte blend. This distinguishes it as a fluid that is primarily used for rehydration rather than electrolyte replacement.