A.Presence of free carbon in exhaust
B.Presence of carbon monoxide in exhaust
C.Presence of oxygen in exhaust
D.Presence of nitrogen in exhaust
E.All of the above
A.Presence of free carbon in exhaust
B.Presence of carbon monoxide in exhaust
C.Presence of oxygen in exhaust
D.Presence of nitrogen in exhaust
E.All of the above