question_answer 16)

                While cooking, if the bottom of the vessel is getting blackened on the outside, it means that (a) the food is not cooked completely                                    (b) the fuel is not burning completely       (c) the fuel is wet                                                           (d) the fuel is burning completely 

Answer:

(b) The fuel is not burning completely. The unbumt particles present in smoke blacken the vessel from outside.