The correct chemical reaction for the given sequence is as follows:

C2H5Br --- (C4H10) Dehydrohalogenation ---> C4H8 --- (C4H6) Dehydrogenation ---> C4H6 --- (CO2) Combustion ---> CO2

Note: The intermediates in the reaction are C4H10 (butane) and C4H8 (1-butene), and the final product is CO2 (carbon dioxide).