Pick out the wrong statement.

A. Strongly caking coal should not be used in the Lurgi gasifier

B. Acetylene gas cannot be used for illumination purpose

C. Water gas is called blue gas because of the color of the flame, when it is burnt

D. Gaseous fuels require less percentage of excess air for combustion as compared to liquid fuels

Please do not use chat terms. Example: avoid using "grt" instead of "great".