Crystalloids are defined as solutions that contain which of the following?

Crystalloids are indeed defined as solutions that contain water and electrolytes. These solutions consist of small molecules that easily pass through cell membranes and are typically used to replace fluid and electrolytes in the body. They are commonly employed in various clinical situations, such as fluid resuscitation or hydration.

The formulation of crystalloids allows for effective distribution in the extracellular space, making them particularly useful in treating conditions like dehydration or hypovolemia. Their composition primarily involves a balance of various electrolytes, such as sodium and potassium, dissolved in water, which mimics the body's natural fluids.

In contrast, solutions that contain large proteins are classified as colloids, while glucose solutions without electrolytes do not fit the definition of crystalloids. Similarly, solutions that consist of fatty substances are classified as lipids and serve different therapeutic purposes. Therefore, water and electrolytes are the key components that characterize crystalloids, making this answer the correct choice.