Which one of the following statements is not true for a supercritical steam generator?
a. It has a very small drum compared to a conventional boiler
b. A supercritical pressure plant has higher efficiency than a sub critical pressure plant
c. The feed pressure required is very high, almost 1.2 to 1.4 times the boiler pressure
d. As it requires absolutely pure feed water, preparation of feed water is more important than in a sub critical pressure boiler