What is the nonliving matrix of connective tissue that allows blood cells to flow?

Plasma is the correct answer as it refers to the liquid component of blood that serves as a nonliving matrix for blood cells. It constitutes about 55% of total blood volume and is primarily composed of water, electrolytes, nutrients, hormones, and waste products. This fluid matrix not only allows red blood cells, white blood cells, and platelets to flow throughout the circulatory system but also facilitates the transport of various substances, including gases, nutrients, and waste materials, to and from the cells of the body.

The interstitium refers to the space between cells in tissues, which is not specific to blood and does not serve as a matrix for blood cells. Collagen is a protein found in connective tissues that provides structural support and strength, and while it plays a significant role in many tissues, it is not involved in forming the matrix that allows the liquid flow of blood cells. Adipose tissue consists of fat cells that store energy and provide insulation, but it is not a component of blood or its matrix. Thus, while all the other choices relate to different aspects of connective or bodily tissues, plasma specifically fits the definition of the nonliving matrix that supports blood cell suspension and flow.