The percentage O₂ by Weight in atmospheric air is

A. improves in summer as compared to that in winter B. improves in winter as compared to that in summer C. is unaffected by climatic conditions D. none of the above

A. less smoke B. more draught C. less chimney gas temperature D. all of the above

A. due to the fact that furnace gases being light go through the chimney giving place to cold air from outside to rush in B. due to the fact that pressure at the grate due to cold column is higher than the pressure at the chimney base due to hot column C. due to the fact that at the chimney top the pressure is more than its environmental pressure D. all of the above

A. when steam is extracted from only one suitable point of steam turbine B. when steam is extracted from several places in different stages of steam turbine C. when steam is extracted only from the last stage of steam turbine D. when steam is extracted only from the first stage of steam turbine