Here's why:

* Plasma is the liquid component of blood, making up about 55% of its volume. It contains water, proteins, electrolytes, and nutrients, including glucose.

* Red blood cells are responsible for carrying oxygen, not glucose.

* White blood cells are part of the immune system and do not directly transport glucose.

* Platelets are involved in blood clotting.

Therefore, glucose is dissolved in the plasma and carried throughout the body.