The internal combustion engine essentially converts fuel and air into carbon dioxide and water. The engine is driven and the heated gases leave it. What is the efficiency of the internal combustion engine? (Several answerc can be correct.) a. Ratio of thermal to freed chemical energy during combustion. b. Ratio of mechanical energy to freed chemical energy in combustion. Ratio of freed chemical energy during combustion to mechanical energy. d. Ratio of thermal to mechanical energy. e. Ratio of mechanical to thermal energy. f. Ratio of freed chemical energy during combustion to thermal energy.