The nonliving matrix of the connective tissue through which the blood cells freely flow is?

A. plasma
B. extracellular fluid
C. intracellular fluid
D. submucosa

The answer to the question is B. extracellular fluid.

To understand why extracellular fluid is the nonliving matrix through which the blood cells flow in connective tissue, let's break down the options:

A. Plasma: Plasma is the liquid component of blood. While it allows for the movement of blood cells, it is not the nonliving matrix within connective tissue.

B. Extracellular fluid: Extracellular fluid refers to the fluid that exists outside the cells in the body. Connective tissue contains extracellular fluid, which acts as the nonliving matrix through which blood cells can freely flow. It provides a space for blood cells to move and circulate.

C. Intracellular fluid: Intracellular fluid is the fluid found within cells, not outside the cells. Therefore, it is not the correct answer in this case.

D. Submucosa: Submucosa is a layer of connective tissue found beneath a mucous membrane. While it does contain blood vessels, it is not the nonliving matrix through which blood cells flow.

Therefore, the correct answer is B. extracellular fluid.