in closed circulatory system blood is enclosed by

Options

A. Tubes
B. Ducts
C. Valves
D. Vessels

Answer

D

Explanation

Circulatory system is of two types :
* Open circulatory system – Blood flows directly in a fluid filled cavity is called open circulatory system.
Ex: In all invertebrates except annelida.
* Closed circulatory system – Blood flows in blood vessels. Ex: In all vertebrates and annelida.