Symptoms show that the combustion in air is necessarily complete

Question

Which of the following symptoms show that the combustion in air is necessarily complete?

 (a) Absence of Oxygen in exhaust

 (b) Absence of Nitrogen in exhaust

 (c) Absence of free carbon in exhaust

 (d) Absence of carbon in exhaust

Comments

absance of free carbon in exhust

Answer 1

C should be answer. Since after full combustion there should be no free carbon and should be in oxidised state. But if carbon monoxide would be in option then it should be carbon monoxide as complete combustion means no more oxidation of fuel. Also as per the question in given year I think option d is " absence of carbon monoxide in exhaust".