In forced circulation type boiler__________________?

A. heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum
B. water is supplied in drum and through down-comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam
C. feed pump is employed to supplement natural circulation in water wall type furnace
D. water is converted into steam in one pass without any recirculation
E. water is heated in a large number of tubes