Final answer:
Plasma is predominantly made up of water, constituting about 90-92% of its composition. The remaining percentage is composed of dissolved substances including proteins, glucose, ions, hormones, and gases.
Step-by-step explanation:
Plasma is the liquid component of blood and makes up about 55% of blood by volume. It is primarily composed of water, making up about 90-92% of plasma. The remaining percentage consists of dissolved substances such as proteins, glucose, ions, hormones, and gases.