Compared to arteries, the velocity of flow of the blood through the capillaries is:.
a) at least 10 times faster.
b) at least twice as fast.
c) about the same.
d) much slower.

D) much slower

Explanation:

The circulatory system, made up of arteries and veins, is fundamental to maintaining life. Its function is the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, the maintenance of physiological pH, and the mobility of the elements, proteins, and cells of the immune system. An artery is each of the vessels that carry blood with oxygen from the heart to the capillaries of the body. They arise from a ventricle and their walls are very strong and elastic to resist the pressure that the blood exerts when it is pumped out of the heart.

Capillaries are very small diameter, thin-walled blood vessels connect small arteries (arterioles) to veins, allowing nutrients and oxygen to pass through to tissues.  The main function of the capillaries is the exchange of substances between the light of the capillaries and the cell interstice of the tissues.

When the blood reaches the capillary bed, the speed with which it circulates inside these vessels is very low. This is due to the fact that in a branching system of tubes, the speed decreases proportionally to the increase in the joint section of the branches. Thus, in the aorta, which has a small section, the speed is very high (400 mm/sec), it decreases at the level of the arteries and arterioles and at the capillary level it becomes minimal (0.1 mm/sec). This fact, together with the thinness of the capillary wall, provides the necessary conditions of time and space for the exchange to take place in the most optimal way.