A.when a fuel is burned in air
B.when a fuel is burned in oxygen
C.when a fuel is burned in air or oxygen
D.when a fuel is burned in air or oxygen without gain or loss of heat
A.when a fuel is burned in air
B.when a fuel is burned in oxygen
C.when a fuel is burned in air or oxygen
D.when a fuel is burned in air or oxygen without gain or loss of heat