What percentage of blood is composed of water?

The correct answer is that approximately 90% of blood is composed of water. Blood is primarily a liquid tissue, and plasma, which makes up about 55% of blood's volume, is mostly water. This high water content is vital for various functions, including the transportation of nutrients, hormones, and waste products, as well as maintaining body temperature and pH balance.

The percentages provided in the other choices do not accurately reflect the composition of blood. While the options suggest significant water content, they fall short of the physiological fact that water constitutes around 90% of blood plasma. Understanding this aspect of blood composition is crucial for comprehending its role in the body and how it supports overall health and homeostasis.