Maximum surface area of circulating system is seen in
a)	Heart	b)	Capillaries	c)	Arterioles	d)	Veins

(b)

Capillaries are microscopic and smallest blood vessels. Their exceedingly thin walls consists of just a thin tunica interna. Most tissues have a rich capillary supply but cartilage and epithelia lack capillaries. Capillaries do not function independently, instead they tend to form interweaving networks called capillary beds. The true capillaries number 10 - 100 per capillary beds depending on the organs or tissues served.